modify windows intall instructions

modify windows intall instructions : direct user to general python download page, and click on big yellow button for version 3.4.1
appropriate version for user's version of windows will be downloaded
Update part-0.ipynb
simplify windows installation

unique procedure for windows 32bits and windows 64bits
the approprite downloaded file is automatically chosen based on the type of the user's OS: 
- python-3.4.1.msi` for win32bits
- python-3.4.1.amd.msi` for win64bits
Update part-0.ipynb
Update part-0.ipynb
Update part-0.ipynb
Merge pull request #42 from pythonsd/part0-win-install

Part0 : simplified windows installation