Merge pull request #114 from iangreenleaf/readme_update

Update Readme to rename "variants" to "alternatives"
Merge pull request #115 from iangreenleaf/control_failover

Fails when Redis is down and loading from config
Uncomment tests
Pull metric tests out of context, do own test init

This avoids problems with trying to change the configuration of a test
that has already been created.
Pull config test out of pre-init block

Same reason as 24c3e7afc5173ab66b3265eafec5d18ed7d7e801.
Big refactoring of Experiment

It's ugly, but it works.

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.
Small test tweaks