This updates the documentation building process to successfully build

docs against Django 1.11 and Python 3.
The biggest set of changes are to the webapidocs extension, which

wasn't at all compatible with Python 3 before. It's now been updated to

use six in place of incompatible value types and methods and to use

correct string types in places.
The Makefile now runs evolve --execute instead of syncdb when

setting up the database. The database file itself is now specified with

an absolute path, which is important for SQLite.
It also fixes up an app name in the initial fixture for the docs build

to use the modern djblets_-prefixed app name required in Django 1.11.

Built the docs under Python 2.7 and 3.7.