Fix issue on 1.8.7
Merge remote-tracking branch 'upstream/master' into super-admin

* upstream/master:
  Fix issue on 1.8.7
Update Twitter Bootsrap 3.0 and fix responsive layout (remove custom width)
Merge branch 'super-admin' of github.com:WaYdotNET/padrino-framework into super-admin

* 'super-admin' of github.com:WaYdotNET/padrino-framework:
  Fixed slim button_to's usage, for some reason the block {} without = wasn't working fine :(. padrino/padrino-framework#1123