Fixed getBranch() when branch name was not URL safe.

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

@@ -86,7 +86,7 @@ public class RepositoryApi extends AbstractApi {
      * @throws GitLabApiException if any exception occurs
      */
     public Branch getBranch(Integer projectId, String branchName) throws GitLabApiException {
-        Response response = get(Response.Status.OK, null, "projects", projectId, "repository", "branches", branchName);
+        Response response = get(Response.Status.OK, null, "projects", projectId, "repository", "branches", urlEncode(branchName));
         return (response.readEntity(Branch.class));
     }