DOC: Linguistic edit to CONTRIBUTING.md
Also fixed a dead link to the Nose testing docs.

Now added.
 cool, pls squash and ping when ready
 Wait a moment, I think the CONTRIBUTING.md file is autogenerated, and the actual source is `doc/source/contributing.rst` (see https://github.com/pydata/pandas/wiki/Regenerating-CONTRIBUTING.md)

@aechase this is a bit inconvenient, but could you redo the changes there?
 Maybe we should also add a comment to `CONTRIBUTING.md` that it is autogenerated to prevent this
 Ah no problem. Perhaps the note about `CONTRIBUTING.md` should go in the "Some other important things to know about the docs" section?
 Yes certainly OK to also mention it somewhere in contributing.rst itself
 @jorisvandenbossche @jreback I notice that `pandas/CONTRIBUTING.md`, `pandas/doc/source/contributing.rst` and http://pandas.pydata.org/pandas-docs/stable/contributing.html are all different. Is the HTML file also built from the `.rst` file or is it separate?

EDIT: sorry, my branch wasn't synced to the master. HTML and `.rst` are consistent, markdown is not (for obvious reasons).
 For the html pages, the link you give if of the latest stable release, so there can be differences. Better look at http://pandas-docs.github.io/pandas-docs-travis/contributing.html which is built for each commit to master.

There can be a deviation between the md and rst file, but that should only be because the md was not regenerated for the last changes to the rst file (this is a manual action).

Conlcusion: you should look at the rst file (and updating the md file by autogenerating it from the latest rst file is always welcome)
 @jreback I think this is ready
 did you see the comment above?

this needs to be edited in `doc/source/contributing.rst` then generated.
 @jreback both are adapted, so I think this is good
 @aechase sorry, didn't see the other file. ok then! ping when you have addressed @jorisvandenbossche comment.
 @jreback @jorisvandenbossche I agree, there ought to be a script for regenerating the Markdown files, but I don't have time to write it today. Happy with these changes?
 Just doing a final check. Where should the following links point?

> An easy way to create a _pandas_ development environment is as follows.
> - Install either :ref:`Install Anaconda <install-anaconda>` or :ref:`Install miniconda <install-miniconda>`

I assume that once upon a time these were links to another section of the document, because the next line refers to `<contributing.forking>`, which still exists. However, there's no obvious section to redirect these two to. Should they become external links to https://www.continuum.io/downloads and http://conda.pydata.org/miniconda.html respectively?
 these should link to a subsection in install.rst 
 @jreback @jorisvandenbossche latest edit now up. Because I used a fresh install of pandoc on this one, the Markdown is showing up as _highly_ edited. You might find the rich diff makes it more clear to see what's actually changed in the `.rst` file.

This edit also fixes the issue #11542.
 Looks good! @aechase this is ready to be merged on your part?

Thanks a lot for this text editing!
 @jorisvandenbossche I'm happy if you're happy!
 And I am happy :-)
 Merging!
 Awesome, now to stop procrastinating on my PR that actually requires coding...
