fix build failure

(https://travis-ci.org/gitlabhq/gitlabhq/builds/3593153)
remove unused code related to gitolite
remove tests for unexisting methods
update grape to 0.3.1 for ruby 2.0 support.

add grape-entity, that is split from grape 0.3.0.
remove usage of deprecated error_format, that is removed in grape 0.2.3.
specs for Gitlab::Popen
specs for api/internal
Fix TestHookContext
move transfer logic out of project to service
fixed popen test
Data converting migrations was wrong. Fixed
Fix project transfer error
API: fix commits pagination

closes #2300
Merge pull request #3095 from fdiary/update-grape-for-ruby2.0

update grape to 0.3.1 for ruby 2.0 support.
proper fix for #2300
Prevent duplicate merge events
Update README
Developers can merge MR if target branch is not protected
use system call to start sidekiq
Merge pull request #3101 from tsl0922/master

Fix project transfer error
Merge pull request #3098 from Undev/important-migrations-fix

IMPORTANT! Data converting in migrations was wrong. Fixed