* factor out Chunk lookup from template tags, put it in the model (so we can use chunks in places other than templates)

* add some formatting for PEP8 compliance
make chunk tag work as assignment tag too
Add a configuration module with default values
factor out default cache time as a setting (so it can be set to non-zero if we want to)
Add template context processor that will add some "common chunks" automatically to template context (so you dont even have to use the chunk tag)
Make it easier to maintain a large list of chunks and make them consistent across several sites
make chunks a little more flexible and easier to call from outside template tags and template context processor