Fixed createPipeline() (#230).

Author: gmessner

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

@@ -183,7 +183,7 @@ public Pipeline getPipeline(int projectId, int pipelineId) throws GitLabApiExcep
     /**
      * Create a pipelines in a project.
      *
-     * POST /projects/:id/pipelines
+     * POST /projects/:id/pipeline
      *
      * @param projectId the project ID to create a pipeline in
      * @param ref reference to commit
@@ -192,7 +192,7 @@ public Pipeline getPipeline(int projectId, int pipelineId) throws GitLabApiExcep
      */
     public Pipeline createPipeline(int projectId, String ref) throws GitLabApiException {
         GitLabApiForm formData = new GitLabApiForm().withParam("ref", ref);
-        Response response = post(Response.Status.CREATED, formData.asMap(), "projects", projectId, "pipelines");
+        Response response = post(Response.Status.CREATED, formData.asMap(), "projects", projectId, "pipeline");
         return (response.readEntity(Pipeline.class));
     }