Add a deploy script

This is mainly just so we don't have to remember the exact incantation
to deploy to staging and production.

To deploy to production, type:

    script/deploy production

To deploy to staging, type:

    script/deploy staging

or just

    script/deploy

(defaults to staging)

The script will deploy whatever branch you currently have checked out.
Merge pull request #41 from troygnichols/deploy-script

Add a deploy script