Ruby support

Hoping to start a discussion on adding Ruby support to Strider. I managed to get something up and running on Heroku reasonably easily using [heroku-buildpack-multi](https://github.com/ddollar/heroku-buildpack-multi). Then I basically just copied strider-python with some fairly minor changes.

The only wrinkle I haven't sorted out yet is that the Ruby buildpack for Heroku sets the `GEM_PATH` environment variable. I have this working on Strider by setting the variable manually with the environments plugin, but suggestions there would be appreciated.