Update mnist.py
Update mnist.py

fix the file reading bug on Windows
comepradz/pybrain,cmorgan/pybrain,tmeits/pybrain,RatulGhosh/pybrain,pybrain/pybrain,pybrain2/pybrain2,zygmuntz/pybrain,jackru/pybrain,luigift/pybrain,luigift/pybrain,tmeits/pybrain,styskin/pybrain,newemailjdm/pybrain,arabenjamin/pybrain,pybrain/pybrain,ii0/pybrain,RatulGhosh/pybrain,sepehr125/pybrain,Adai0808/pybrain,comepradz/pybrain,RafaelCosman/pybrain,zygmuntz/pybrain,styskin/pybrain,taylorhxu/pybrain,garyfeng/pybrain,chanderbgoel/pybrain,yonglehou/pybrain,Adai0808/pybrain,comepradz/pybrain,jlegendary/pybrain,newemailjdm/pybrain,sepehr125/pybrain,newemailjdm/pybrain,arabenjamin/pybrain,taylorhxu/pybrain,Adai0808/pybrain,jackru/pybrain,luigift/pybrain,blueburningcoder/pybrain,blueburningcoder/pybrain,RafaelCosman/pybrain,samstern/MSc-Project,styskin/pybrain,Neural-Network/TicTacToe,chanderbgoel/pybrain,yonglehou/pybrain,CVML/pybrain,blueburningcoder/pybrain,garyfeng/pybrain,pybrain/pybrain,RafaelCosman/pybrain,yonglehou/pybrain,jackru/pybrain,pybrain2/pybrain2,zygmuntz/pybrain,cmorgan/pybrain,Neural-Network/TicTacToe,zygmuntz/pybrain,chanderbgoel/pybrain,taylorhxu/pybrain,arabenjamin/pybrain,ii0/pybrain,jlegendary/pybrain,Ryanglambert/pybrain,CVML/pybrain,cmorgan/pybrain,pybrain2/pybrain2,ii0/pybrain,jlegendary/pybrain,Neural-Network/TicTacToe,RatulGhosh/pybrain,sepehr125/pybrain,tmeits/pybrain,Ryanglambert/pybrain,Ryanglambert/pybrain,garyfeng/pybrain,CVML/pybrain