Update 20130419190306_allow_merges_for_forks.rb

Postgress db migrate fails.(5.4=>6.0)
Fixed 500 error when try to remove group
Merge pull request #4862 from dsekretov/patch-1

Update 20130419190306_allow_merges_for_forks.rb
Merge branch '6-0-stable' into 6-0-admaster