Added a section on using setup.py develop.  This will provide a good segue into talking about virtualenv. Will also add the suggested docs for trying out a PR
Added a basic overview of using virtualenv
Add some notes on virtualenvwrapper and venv; fix some minor sphinx syntax issues
Here are some additional notes on using virtualenv with IPython
Got rid of references to './setup.py' per @astrofrog's comments. I still used to just 'setup.py foo' when referencing specific setup.py commands, but wrote out 'python setup.py' when discussing full commands run at the command line.
As Tom pointed out, this functionality is built into IPython as of 0.13, so make note of that. Still worth keeping the steps documented though--enough people are still on older IPython versions
Merge pull request #343 from iguananaut/issue-343

Document how to try out a pull request in a virtualenv