remove __future__ imports from documentation
THE FUTURE IS NOW

Warehouse is a Python 3 project now
Merge pull request #255 from ewdurbin/future_is_now

remove __future__ imports
Spin up our own PostgreSQL server and use it
Add a marker for any test that uses the database
Create an escape hatch for using an existing database
Merge pull request #258 from dstufft/rework-database

Reworking database fixtures
Cache the loaded assets.json

This will allow us to avoid hitting the disk everytime we need
to create a static file URL.
Cleanly shutdown PostgreSQL with SIGINT instead of SIGKILL
Merge pull request #259 from dstufft/cache-assets-json

Cache the loaded assets.json
Merge pull request #260 from dstufft/cleanly-shutdown-postgresql

Cleanly shutdown PostgreSQL with SIGINT instead of SIGKILL