Gemify Ruby Library

Introduces this repo as a Ruby gem. This adds some really nice stuff, such as testing, versioning, depedencies, etc. This drastically eases its use in other projects.

I'm explicitly keeping the oAuth tokens hidden for now. Until we either hear word of an official program for getting them, or Tesla OK's the use of the ones from the app (very unlikely), I'll keep them that way. I really don't want to be rude to Tesla and force them to issue a C&D. This API is a privilege, not a right. Play nicely :smile: