Run tasks as the collins user.
If no user is passed, run as the current user, not as 'collins'.

In conjunction with the changes to the deploy cap script, this will still result in the collins process being run by the collins user.
Reverted the 'sudo' blocks to 'run' blocks.
Run as 'deploy' user, not 'root'.
Merge pull request #136 from tumblr/will-deploy-as-collins

Deploy as deploy user