Basic integration of Sift Science.

This integrates Sift Science's Javascript snippet and a REST API call for transactions. There are many more custom events we could send for charges, ACH transfers, etc., but this is enough to get started.

The instructions for using "make run" and "make test" don't seem to work for me at the moment -- I keep getting postgres authentication errors. I tried to test the new code by running it in isolation, but if you have a working setup, it'd be wise to do some spot checking before merging.

Also, note that you have to define an environment variable SIFT_SCIENCE_API_KEY with the secret key I sent you separately. I didn't want to put that value in locals.env since it would open up a potential way for fraudsters to manipulate the system by sending fake data.