API documentation updated for project snippets.

The API Documentation for project snippets got infos to return codes. Tests are added
to check status codes when handling project snippets.

spec/requests/api/projects_spec.rb

@@ -480,6 +480,11 @@ describe Gitlab::API do
       json_response.should be_an Array
       json_response.first['title'].should == snippet.title
     end
+
+    it "should return 401 error if user not authenticated" do
+      get api("/projects/#{project.id}/snippets")
+      response.status.should == 401
+    end
   end
 
   describe "GET /projects/:id/snippets/:snippet_id" do
@@ -520,6 +525,12 @@ describe Gitlab::API do
         title: 'api test', file_name: 'sample.rb'
       response.status.should == 400
     end
+
+    it "should return a 401 error if user not authenticated" do
+      post api("/projects/#{project.id}/snippets"),
+        title: 'api test', file_name: 'sample.rb', code: 'i=0'
+      response.status.should == 401
+    end
   end
 
   describe "PUT /projects/:id/snippets/:shippet_id" do