Repository Reorganization

Beginning GitHub repository reorganization suggested [here](https://gist.github.com/akalicki/8b72148802a3c4fa0880) (PHP port will come in a separate PR).
- [x] moved main Python code, README, setup script, + docs to new `python` directory
- [x] moved ruby implementation to `alpha` directory

TODO:
- [ ] write new, more general README for repository reflecting updated code organization

Let me know if this is what you were thinking!