Add create_tag method. Add tests for new method.

lib/gitlab/client/repositories.rb

@@ -16,6 +16,20 @@ def tags(project, options={})
     end
     alias_method :repo_tags, :tags
 
+    # Creates a new project repository tag.
+    #
+    # @example
+    #   Gitlab.create_tag(42,'new_tag','master'))
+    #
+    # @param  [Integer] project The ID of a project.
+    # @param  [String]  tag_name The name of the new tag.
+    # @param  [String]  ref The ref (commit sha, branch name, or another tag) the tag will point to.
+    # @return [Gitlab::ObjectifiedHash]
+    def create_tag(project, tag_name, ref)
+      post("/projects/#{project}/repository/tags", body: {tag_name: tag_name, ref: ref})
+    end
+    alias_method :repo_create_tag, :create_tag
+
     # Gets a list of project commits.
     #
     # @example

spec/fixtures/tag.json

@@ -0,0 +1 @@
+{"name": "v1.0.0","commit": {"id": "2695effb5807a22ff3d138d593fd856244e155e7","parents": [],"message": "Initial commit","authored_date": "2012-05-28T04:42:42-07:00","author_name": "John Smith","author email": "john@example.com","committer_name": "Jack Smith","committed_date": "2012-05-28T04:42:42-07:00","committer_email": "jack@example.com"},"protected": false}

spec/gitlab/client/repositories_spec.rb

@@ -2,6 +2,7 @@
 
 describe Gitlab::Client do
   it { should respond_to :repo_tags }
+  it { should respond_to :repo_create_tag }
   it { should respond_to :repo_branches }
   it { should respond_to :repo_branch }
   it { should respond_to :repo_commits }
@@ -24,6 +25,21 @@
     end
   end
 
+  describe ".create_tag" do
+    before do
+      stub_post("/projects/3/repository/tags", "tag")
+      @tag = Gitlab.create_tag(3,'v1.0.0','2695effb5807a22ff3d138d593fd856244e155e7')
+    end
+
+    it "should get the correct resource" do
+      a_post("/projects/3/repository/tags").should have_been_made
+    end
+
+    it "should return information about a new repository tag" do
+      @tag.name.should == 'v1.0.0'
+    end
+  end
+
   describe ".commits" do
     before do
       stub_get("/projects/3/repository/commits", "project_commits").