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Merge commit '551e7be19fee7e88adb42f9a58d68b025f451a8a'

* commit '551e7be19fee7e88adb42f9a58d68b025f451a8a':
  Downgraded rails :(
  Switch to new scope syntax
change some style issues, and add solution controller, delete useless preference controller
Merge remote-tracking branch 'zhen/master'