DOC: review installation instructions

[jreback]

xref #7849

[lexual]

Ping?

What did we what do discuss further?

[jorisvandenbossche]

I think it is mainly on my comments there (#7849 (comment)):

I was just wondering if the focus is a bit too much on Anaconda? I myself also use it, and I would also recommend this personally to others, but as 'pandas' we should maybe be a bit more neutral. As there are also other 'distributions' that you can use to get the full scipy/pydata stack (enthought canopy, pythonxy, ..).
Maybe we should do more something like on http://www.scipy.org/install.html: list some different scientific python distributions, and then we can still elaborate more on how to use it with Anaconda?

On the 'neutrality' issue, I agree we should provide clear and easy instruction (and therefore, we (should) also recommenend to use distributions instead of installing it manually (as now with your PR)).
But you have also the other side: eg Enthought also has done a lot for the numpy/scipy community, and they maybe would appreciate it we list them (in fact, they are mentioned now, at the end of the dependencies section). @jreback @cpcloud What do you think?