Some additional fixes after Jinja2 integration
Cleanup: source is never None
Cleanup: Get rid of two simple functions

Actually there is no need for them.
Import cleanup: Explicitly import stuff

Also remove unused import. Previously it was hard to notice that it
was no longer necessary. This is why explicit is better than implicit.
Minor cleanups: Remove unnecessary assignments
Cleanup: Unwrap parameters
Cleanup: Remove some unnecessary blank lines
More imports cleanups
Minor changes to ease further changes
Merge pull request #84 from unho/some-cleanups

More cleanups