-----------------------
Added:
* Add ``ConfigEnvFileEnv`` for supporting ``.env`` files. Thank you, Paul!
* Add "on" and "off" as valid boolean values. This makes it easier to use config
for feature flippers. Thank you, Paul!
Changed:
* Change ``ConfigIniEnv`` to take a single path or list of paths. Thank you,
Paul!
* Make ``NO_VALUE`` falsy.
Fixed:
* Fix ``__call__`` returning None--it should return ``NO_VALUE``.
Lots of docs updates: finished the section about making your own parsers, added
a section on using dj-database-url, added a section on django-cache-url and
expanded on existing examples.