Start combining various development documentation into one place.
Closes #6232 

In working with the various "Contributing" documents recently it was clear that we needed to combine them.  This is a stab at doing so.  I took the various components from pydata.org, CONTRIBUTING.md, various wiki pages, and the already included Documentation documents and created this file.  I think it's a good start.

@rockg this is pretty awesome!

I would like to emphasize test driven development (TDD)
eg write a test to reproduce where test fails , fix code, then test passes
so maybe move testing a bit higher
 I tried to keep things in order of how they are done.  I think it makes sense where it is in the document--after building the code and before committing.  I can put some mention of it at the top in the "working with code" section and make it more explicit in the testing section.  Would that work?
 lgtm. @jorisvandenbossche @shoyer 
 Indeed, thanks @rockg !
 With this I would like to redirect http://pandas.pydata.org/developers.html and https://github.com/pydata/pandas/blob/master/CONTRIBUTING.md to this page.  Does that sound good? I think CONTRIBUTING.md is what is linked when making a new pull request (something like "Please read the following guidelines...").  Is it possible to have something else show up in that message, e.g., a list of things, or can it only point to this file?
 I'm pretty sure the GitHub link can only point to the file with that name.

On Thu, Apr 2, 2015 at 4:40 PM, rockg notifications@github.com wrote:

> With this I would like to redirect
> http://pandas.pydata.org/developers.html and
> https://github.com/pydata/pandas/blob/master/CONTRIBUTING.md to this
> page. Does that sound good? I think CONTRIBUTING.md is what is linked when
> making a new pull request (something like "Please read the following
> guidelines..."). Is it possible to have something else show up in that
> message, e.g., a list of things, or can it only point to this file?
> 
> —
> Reply to this email directly or view it on GitHub
> https://github.com/pydata/pandas/pull/9754#issuecomment-89080159.
 I can change the developers links to just about anything

ok let's merge and I'll fix the link tonight

then we can review everything and fix if needed
 I think we might need to link CONTRIBUTING.md to the dev page for this to work
 "dev page" is the page added for this PR, right?  If so, yes, I think this is what we want.  And then we llink the developers from pydata to the docs page as well.
 yep
 Better yet, probably link to "Contributing to the code base"
 @rockg Wow, this is great!
 http://pandas.pydata.org/index.html

is updated (the About Pandas / Contributing Guidelines link), currently goes to the dev docs.
