Added export functionality

For now it's only upstart, but other exports can be added as needed
Added MANIFEST, updated setup.py to include data
Add export --shell argument
Cleanup export
Merge pull request #1 from Birdback/master

Adds export --shell argument
Add export functionality.

Merge branch 'master' of git://github.com/flashingpumpkin/honcho into master
Minor stylistic tweaks to export functionality
Don't assume user gid == user uid

There's no reason the user's primary group gid should be the same as their
uid.