testris: flatten diff output into a string instead of a list
testris: flatten diff output into a string instead of a list

bschaef14/learntris,Shamash2014/spice_and_html,DTSCode/learntris-haskell,TylerLau/learntris,Larsharaldjoh/Tetris,LearnProgramming/learntris,nbgraham/learntris,tangentstorm/learntris,geugon/learntris,Shamash2014/spice_and_html,BigRoss/learntris,BigRoss/learntris,mosegontar/learntris,TylerLau/learntris,SultansDream/testris,bschaef14/learntris,WhitmanH/learntris,bschaef14/learntris,Shamash2014/spice_and_html,lochanaeg/learntris