Merge pull request #350 from ke-pan/master

when update reply, last_reply_usr_id should not be change
user_name_tag user.class == ''.class => user.is_a? String
Merge branch 'master' of github.com:ruby-china/ruby-china
Gems config files upto Rails 4.2.0
Use partial template to instead Cells
Devise upgrade to GitHub master, to fix with Rails 4.2, all test cases work fine.
Update readme.
Disable config.assets.debug, this will slow down all requests.
Fix user bar dropdown.
remove quiet_assets gem
update gem source
Wiki index without sanitize custom html
use raw instead of sanitize to make topic time info appear