Update configuration to support easier deployment

* GOAL: Let the deployment process write one config file, and provide an easy
  env path for loading that config in
* Add `FIRETRACKER_CONFIG_PATH` env, which specifies the config file to load
* Prefer "production" settings, but add the ability to turn on debug via a
  flag in the config (other debug stuff could go in there as well)
* Remove the funky interpreter stuff from passenger_wsgi. I believe this was
  to support per-virtualenv python versions, which I don't believe we will
  be using (and could probably implement a different way)
* Config files don't need to support multiple environments, since we write
  them out specific to the environment
updates git ignore to keep .yml files out of repo
adds sample yml config file
adjust requirements file
Merge pull request #183 from SCPR/ConfigUpdates

Update configuration to support easier deployment