Implementing passing AC/WA info using flash.
Add message methods to Problem model
Add a message to flash[:solved] according to AC/WA
Display AC/WA message in problem page after submission
Make message methods instance methods to make them more flexible
Make the View responsible for, well, the view.
Merge pull request #51 from TakenokoChocoHolic/2_Show_ACWA

2 show acwa