Updating for enhanced MySQL support

[scotthavens]

Mainly changes to incorporate using MySQL as a storage backend and a few minor updates to Redis. To accomplish the update, I made some fairly sizeable changes to the project structure to facilitate.

Changes

• moved flask_test_usage out of the src directory as it was causing problems for me
• The pip redis package was updated to version 3. redis does not interpret the data anymore but relies on the user, so using json to store and retrieve dict objects
• The project I'm using this for uses the flask factory which required some updates to track_usage.init_app
• Added the track_var to the sqlstorage hooks
• Used pipenv for managing packages, may want to ignore these based on how the distribution is setup

[scotthavens]

I was a little early, it's not quite ready. It worked with testing but it didn't work out in the wild.

[ashcrow]

No problem. Thanks for opening this. I'm happy to review in progress if/when you open a new PR :smiley:.