Allow config file at ~/.trellish
Add "start" and "finish" commands

If you don't specify a card id/URL on the command
line, we fetch the list of cards from Trello and
we ask the user to pick one.
Update README
Cleanup
Announce start/finish in Campfire
Update readme
Improve start/finish messages
Improve error handling
Add a card comment containing the pull request URL

It seems that updating the card's description
changes the card's URL. This breaks the links
we put in our Github Pull Request and the link
we put to Campfire. As a workaround, add a comment
instead.
Before finishing, confirm remote is up-to-date
Use rev-parse to determine the git directory
Sort methods
Bump version