Fix #38: add FREEZER_STATIC_IGNORE config option.

Allows you to stop certain static files (anything served by
send_static_file) from being built with your project based
on a list of fnmatch style patterns. Had to add a main.js
static file to the test app and change the test_all_urls_method
to work with the built_app context manager.
Merge pull request #39 from HeyImAlex/static_ignore

Add FREEZER_STATIC_IGNORE config option.