PEP8 fix to mnist demo.
PEP8 fix to mnist demo.

takacsg84/Lasagne,mheilman/Lasagne,DataFighter/Lasagne-tutorial,Richi91/nntools,dnuffer/Lasagne,rlkelly/Lasagne,DeanChan/Lasagne,ErnstHowie/Lasagne,ebattenberg/Lasagne,MihailoIsakov/fishfish,gabortakacs/Lasagne,cancan101/Lasagne,kracwarlock/Lasagne