`emp run` could take a release argument

[hamiltop]

Sometimes a full deploy is overkill when you just want to run a little snippet of code via rails c or something. By specifying a release, one could avoid having to deploy everywhere.

It would be especially useful in shared development/staging environments.

[sanjayprabhu]

Even more generally, it should take a SHA. That way you can run scripts that have not been merged (e.g. test code that hasn't been been merged yet without taking over the whole environment). Probably need to be able to disable the SHA support because you may not want to allow this on production.