Refactoring Experiment

Here's the refactoring of the `Experiment` class that I mentioned. The primary goal is to have `new`, `find`, and `find_or_create` all behave in an appropriate manner. Config files are used to initialize values, but not in place of the Redis store.

I also took the opportunity to clean a bunch of stuff up and shuffle things around a little bit.

There are a couple more things I might do if I have time, but it's pretty much ready as it is.