PyCon 2014 Sprint Additions

1. Add 'Required Background Knowledge' section
2. Add instructions on using virtual environments
3. Minor syntax updates
Add reference to CONTRIBUTING.rst in edx-platform repo.
Add Mike Dunn <mike@eikonomega.com>
Merge branch 'master' of https://github.com/eikonomega/XBlock

Conflicts:
	doc/getting_started.rst