add virtualenvwrapper presentation

presentation delivered on March 27, 2013

This is the markdown used during the presentation (by themselves are incomplete,
 they were kind of like slides in that they were designed by be complimentary
 to speaking).

Since then, I've added the Getting Started section
Merge pull request #4 from chrishiestand/master

add virtualenvwrapper presentation
Merge branch 'master' of github.com:pythonsd/presentations