Feature: reopen closed merge request

Signed-off-by: Dmitriy Zaporozhets <dmitriy.zaporozhets@gmail.com>
Add tests to reopen MR

Signed-off-by: Dmitriy Zaporozhets <dmitriy.zaporozhets@gmail.com>
 Merge branch 'feature/reopen_mr' into 'master'

Feature: reopen closed merge request
Merge branch 'master' of github.com:gitlabhq/gitlabhq