Everett

-----------------------

Added:

* Add ``ConfigManager.from_dict()`` shorthand for building configuration
instances.

* Add ``.get_namespace()`` to ``ConfigManager`` and friends for getting
the complete namespace for a given config instance as a list of strings.

* Add ``alternate_keys`` to config call. This lets you specify a list of keys in
order to try if the primary key doesn't find a value. This is helpful for
deprecating keys that you used to use in a backwards-compatible way.

* Add ``root:`` prefix to keys allowing you to look outside of the current
namespace and at the configuration root for configuration values.

Changed:

* Make ``ConfigDictEnv`` case-insensitive to keys and namespaces.

Documentation fixes and updates.

-----------------------

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.

----------------------

Initial writing.