Add optional ./deploy <env> param to allow mutliple environment

By default, `./deploy <env>` will use a `git remote` called
`deploy_<env>`. In cases where there may be multiple remotes for the
same RAILS_ENV, specify `./deploy <env> <titbit>` where the git remote
is `deploy_<titbit>`
Merge pull request #58 from anchor/deploy_env

Add optional ./deploy <env> param to allow mutliple environment