Fixed issues related to HTTP status (#29, #31).

src/main/java/org/gitlab4j/api/GroupApi.java

 package org.gitlab4j.api;
 
+import org.gitlab4j.api.GitLabApi.ApiVersion;
 import org.gitlab4j.api.models.Group;
 import org.gitlab4j.api.models.Member;
 import org.gitlab4j.api.models.Project;
@@ -167,7 +168,8 @@ public class GroupApi extends AbstractApi {
             throw new RuntimeException("groupId cannot be null");
         }
 
-        delete(Response.Status.OK, null, "groups", groupId);
+        Response.Status expectedStatus = (isApiVersion(ApiVersion.V3) ? Response.Status.OK : Response.Status.NO_CONTENT);
+        delete(expectedStatus, null, "groups", groupId);
     }
 
     /**
@@ -213,7 +215,7 @@ public class GroupApi extends AbstractApi {
         Form formData = new Form();
         formData.param("user_id", userId.toString());
         formData.param("access_level", accessLevel.toString());
-        Response response = post(Response.Status.OK, formData, "groups", groupId, "members");
+        Response response = post(Response.Status.CREATED, formData, "groups", groupId, "members");
         return (response.readEntity(Member.class));
     }
 
@@ -227,6 +229,7 @@ public class GroupApi extends AbstractApi {
      * @throws GitLabApiException if any exception occurs
      */
     public void removeMember(Integer projectId, Integer userId) throws GitLabApiException {
-        delete(Response.Status.OK, null, "groups", projectId, "members", userId);
+        Response.Status expectedStatus = (isApiVersion(ApiVersion.V3) ? Response.Status.OK : Response.Status.NO_CONTENT);
+        delete(expectedStatus, null, "groups", projectId, "members", userId);
     }
 }
\ No newline at end of file

src/main/java/org/gitlab4j/api/ProjectApi.java

@@ -568,7 +568,8 @@ public class ProjectApi extends AbstractApi implements Constants {
      * @throws GitLabApiException if any exception occurs
      */
     public void removeMember(Integer projectId, Integer userId) throws GitLabApiException {
-        delete(Response.Status.OK, null, "projects", projectId, "members", userId);
+        Response.Status expectedStatus = (isApiVersion(ApiVersion.V3) ? Response.Status.OK : Response.Status.NO_CONTENT);
+        delete(expectedStatus, null, "projects", projectId, "members", userId);
     }
 
     /**
@@ -765,7 +766,8 @@ public class ProjectApi extends AbstractApi implements Constants {
      * @throws GitLabApiException if any exception occurs
      */
     public void deleteHook(Integer projectId, Integer hookId) throws GitLabApiException {
-        delete(Response.Status.OK, null, "projects", projectId, "hooks", hookId);
+        Response.Status expectedStatus = (isApiVersion(ApiVersion.V3) ? Response.Status.OK : Response.Status.NO_CONTENT);
+        delete(expectedStatus, null, "projects", projectId, "hooks", hookId);
     }
 
     /**

src/main/java/org/gitlab4j/api/RepositoryApi.java

@@ -204,7 +204,8 @@ public class RepositoryApi extends AbstractApi {
      * @throws GitLabApiException if any exception occurs
      */
     public void deleteTag(Integer projectId, String tagName) throws GitLabApiException {
-        delete(Response.Status.OK, null, "projects", projectId, "repository", "tags", tagName);
+        Response.Status expectedStatus = (isApiVersion(ApiVersion.V3) ? Response.Status.OK : Response.Status.NO_CONTENT);
+        delete(expectedStatus, null, "projects", projectId, "repository", "tags", tagName);
     }
 
     /**

src/main/java/org/gitlab4j/api/RepositoryFileApi.java

@@ -133,7 +133,8 @@ public class RepositoryFileApi extends AbstractApi {
         addFormParam(form, "file_path", filePath, true);
         addFormParam(form, isApiVersion(ApiVersion.V3) ? "branch_name" : "branch", branchName, true);
         addFormParam(form, "commit_message", commitMessage, true);
-        delete(Response.Status.OK, form.asMap(), "projects", projectId, "repository", "files");
+        Response.Status expectedStatus = (isApiVersion(ApiVersion.V3) ? Response.Status.OK : Response.Status.NO_CONTENT);
+        delete(expectedStatus, form.asMap(), "projects", projectId, "repository", "files");
     }
 
     private Form file2form(RepositoryFile file, String branchName, String commitMessage) {

src/main/java/org/gitlab4j/api/ServicesApi.java

@@ -3,6 +3,7 @@ package org.gitlab4j.api;
 import javax.ws.rs.core.Form;
 import javax.ws.rs.core.Response;
 
+import org.gitlab4j.api.GitLabApi.ApiVersion;
 import org.gitlab4j.api.models.Project;
 
 /**
@@ -55,7 +56,8 @@ public class ServicesApi extends AbstractApi {
      * @throws GitLabApiException if any exception occurs
      */
     public void deleteGitLabCI(Integer projectId) throws GitLabApiException {
-        delete(Response.Status.OK, null, "projects", projectId, "services", "gitlab-ci");
+        Response.Status expectedStatus = (isApiVersion(ApiVersion.V3) ? Response.Status.OK : Response.Status.NO_CONTENT);
+        delete(expectedStatus, null, "projects", projectId, "services", "gitlab-ci");
     }
 
     /**
@@ -110,7 +112,8 @@ public class ServicesApi extends AbstractApi {
      * @throws GitLabApiException if any exception occurs
      */
     public void deleteHipChat(Integer projectId) throws GitLabApiException {
-        delete(Response.Status.OK, null, "projects", projectId, "services", "hipchat");
+        Response.Status expectedStatus = (isApiVersion(ApiVersion.V3) ? Response.Status.OK : Response.Status.NO_CONTENT);
+        delete(expectedStatus, null, "projects", projectId, "services", "hipchat");
     }
 
     /**

src/main/java/org/gitlab4j/api/UserApi.java

@@ -6,6 +6,7 @@ import javax.ws.rs.core.Form;
 import javax.ws.rs.core.GenericType;
 import javax.ws.rs.core.Response;
 
+import org.gitlab4j.api.GitLabApi.ApiVersion;
 import org.gitlab4j.api.models.User;
 
 /**
@@ -159,7 +160,8 @@ public class UserApi extends AbstractApi {
             throw new RuntimeException("userId cannot be null");
         }
 
-        delete(Response.Status.OK, null, "users", userId);
+        Response.Status expectedStatus = (isApiVersion(ApiVersion.V3) ? Response.Status.OK : Response.Status.NO_CONTENT);
+        delete(expectedStatus, null, "users", userId);
     }
 
     /**