Restructure front documentation page to emphasize contributions rather than development
Example of reworked documentation aimed at beginners
Clarify language in several places
Change line breaks to keep length under 80 characters
Fix typographical errors
Add caveats about cases when setup.py develop will fail
Clarify warning about need to reactive development astropy

New wording suggested by @mdboom
Fix line that was too long
Add summary of virtual environment commands for anaconda and virtualenvwrapper
Condense git installation/configuration instructions
Fix typographic errors
Minor wording changes and link updates
Add link to git basics
Update thumbnail of fork button on github
Replace git/GitHub installation and configuration with link to separate document
Separate guidelines from workflow
Update thumbnails of github interface
Add labels for cross-referencing
Move virtualenv information to a separate document
Move new contributing docs into workflow folder