Fix an ERROR in Gemfile
Fix an ERROR in Gemfile

FriendlyID has already remove the branch 'rails4', and now the branch 'master' is working under rails4
xuewenfei/photographer-io,laputaer/photographer-io,xuewenfei/photographer-io,wangjun/photographer-io,arnkorty/photographer-io,robotmay/photographer-io,robotmay/photographer-io,xuewenfei/photographer-io,damoguyan8844/photographer-io,wangjun/photographer-io,robotmay/photographer-io,arnkorty/photographer-io,damoguyan8844/photographer-io,laputaer/photographer-io,wangjun/photographer-io,laputaer/photographer-io,arnkorty/photographer-io,damoguyan8844/photographer-io