Bring deploy code up to parity w/ Capistrano 2.15.5

I know that leehambley/railsless-deploy is obsolete, but I ended up hacking this together to fix an issue for myself while I'm still transitioning to Cap 3.

The biggest fix here is for `run_locally`, see [lib/railsless-deploy.rb at line 126](#diff-52e0e27ca58cdf18fd06c0f9ee11e664R126) for details.

Otherwise, it's just ensuring that no other idiosyncrasies exist between vanilla Cap & railsless-deploy (other than what's by design, of course).