Allow creating a static view and setting cache-control/expires headers

In this pull request the functionality to register your static assets as a static view with Pyramid is added back in, using the configuration setting `static_view`, and a static view's cache-control and expires headers may be set using the configuration setting `cache_max_age`.

Documentation is updated, and two very basic tests to confirm the presence of these settings in the environment object are present. I've further changed some hardcoded directory locations in the tests to os.getcwd().

I've also ignored an error raised when one calls render() on a template outside of a request, e.g., to compile static assets before the first request is made.