Modernize Python App 

* Correct code formatting to PEP8 specification
* Allow using custom redis backend
* Allow custom rate
* Move python files to subdirectory, to make published python package

I went ahead and published this as `forgettable` [on PyPi](https://pypi.python.org/pypi/forgettable), because I am using it currently with an external project and couldn't wait for this to be merged and you guys to publish it. I am happy to hand overship of that python package to anyone who wants it.