Python 2.6 compatibility and asset inclusion when installing as a package

A few quick fixes I needed on a production deployment of pypicache, mostly trivial.

Firstly, because recent versions of Debian are still stuck on Python 2.6.6, I needed to add positional argument specifiers.

Secondly, because we need to install everything as a package, I had to include the package data locations in the setup.py file. Unfortunately specifying them in the manifest isn't enough unless you're deploying into a virtual environment using 'python setup.py develop' or the like. That includes them in the distribution tarball, but they won't be installed.