Ability to permanently set environment variables

[johnnyschneider]

As far as I can tell based off of usage, this application does not permanently set environment variables after exiting shell environment - on Windows, anyways. I suggest using penv for this. Specifically, in use.go, we could modify lines 68-70 to include SetEnv from penv. I'm struggling to understand the entirety of the use.go file (new to go) but if I knew how to build, I think I could write a prototype for code review.