Kill flask

This is dependent on #228 -- I built off of that to avoid merge conflicts later. Let's get that merged first.

As stated in the last commit, the logic isn't that different - it's pretty much what you get when you un-nest all of the decorators. It's a good bit cleaner now, and removes our dependency on flask, which is nice for a couple reasons:

* Flask pulls in a lot of dependencies, mnostly things like Jinja2 that we aren't using
* Flask does some things that make usage in multi-threaded/forking environments tricky to think about -- the new implementation is pretty straightforward in that regard.

This needs careful testing, but lets start the review now.
Why is this file in this pull request?