Py2 compatability has been broke elsewhere drop it

This is all noop in Py3, and Py2 is broke now in various places.
Dropping Py2 code as it will not be a thing going forward.

Django 2 is the next release, Py2 support will be dropped, as such,
dropping this is forward looking.

Massively upgrade symposion

* Remove markitup (to be replaced with Ace editor)
* Use DUA decorators
* Removed custom signup bits
* Upgraded dependencies
* Added migrations
* Namespaced template locations
* Removed html5parser/sanitizer (for now) - parsing functionality
should be moved out entirely to a hooks
* Replaced ProposalScoreExpression object with a function that returns
F() expressions

Remove migrations

These migrations were written for South. Now that we have Django 1.7,
we will just use Django migrations once we hit a 1.0 release.