Some tidying, added a negative test, method tests.

The latter was because the new feature was not actually conditional on its
compiler parameter. It was on all the time.
Moved falsey-ness detection into compiler.

Fixes #39.

This fixes a bug where falsey values were not properly triggering inverted
sections, and consolidates some logic.

Also did some renaming. Couldn't help myself.
User-extensible escaping rules (not just HTML or no escaping)
README describes user-extensible escaping rules (not just HTML or no escaping)
Fixed formatting in README
Reworked user-defined escaping to suit my tastes.
Fixed source headers.
Some javadoc improvements.
Access array item by index in templates