DOC/DEV: update windows instructions for setting up dev environment for py3

[Vutsuak16]

I am trying to set up a development environment for pandas in anaconda.
But I get the following error, while installing dependencies for windows:-
on running "conda install -n pandas_dev libpython"

Error: Unsatisfiable package specifications.
Hint: the following packages conflict with each other:

• libpython
• python 3.5*

is conda not compatible with python 3.5??

[jreback]

libpython is only necessary for py2 on Windows
the conda recipe knows this but requirements.txt does not
I suppose this could be updated in the docs

[Vutsuak16]

@jreback i could update the docs , but the doc build won't work for sphinx version >1.3 . Mine is 1.3.1
When would this issue be solved??

[jreback]

iirc try a newer version of Sphinx / 1.3.3 works

[jreback]

note if on Windows u actually need to have a visual studio installed (for py3) so these instructions are a bit more complicated

[Vutsuak16]

well yeah and for python version>= 3.5 we actually need vc 2015

[jreback]

yeah these are a bit more work to setup
ideally we would have links directly to what u need to install (everything is free)

[Vutsuak16]

yeah I would love to work on updating the docs. Just created a whole development environment on windows to edit docs, gave me hell of a time. Don't want other people to face that