Fix an ERROR in Gemfile

FriendlyID has already remove the branch 'rails4', and now the branch 'master' is working under rails4
Merge pull request #156 from cassiuschen/patch-1

Switch to master branch for FriendlyID gem
Adjust collection sorting
Merge pull request #157 from robotmay/collection-sorting-adjustment

Hotfixes and collection sorting adjustment
Merge remote-tracking branch 'upstream/master'