Django-local-settings

- Added support for Python 3.7.
- Fixed regression in 1.0b8 that causes spaces around names in
interpolation groups to throw an error.
- Made various changes to internals to better support loading from alternative
types of settings files, YAML in particular (which is a work-in-progress in
a separate branch).
- Default local settings file is now discovered based on supported file
types instead of unconditionally using "local.cfg".
- The settings file loading strategy is now based on the name of the specified
local settings file instead of unconditionally using the INI/JSON loading
strategy.
- Mutable vs. non-mutable mappings are now handled separately when
interpolating.
- Simplified internals of loader, esp. wrt. decoding values & interpolation.

- Added a mechanism for deleting settings via the `DELETE` setting (a
list containing dotted paths of settings to remove). This can be used
to remove settings that are common to most environments from a special
environment (such as testing).
- Added `Settings.pop_dotted()` (this was actually added to
`DottedAccessMixin`, but it's normally used via `Settings`).
- Updated settings path-parsing internals to use a stack.
- Updated settings injection/interpolation logic to use a stack.
- The previous two items enable nested interpolation in settings paths
and values (like `{{X.{{Y}}}}`).
- When a member of a list-type setting isn't found, an `IndexError` will
now be raised. Previously, the `IndexError` would be caught and
a `KeyError` would be raised instead, but that's incosistent and could
be confusing.

- [4] Fixed a bug with loading/interpolation of tuples (and other non-mutable
sequences).
- Declared official support for Django 1.11.

- Enable interpolation of all types of settings values, not just strings. For
example, the following now works as expected:

ITEMS = ["a", "b", "c"]
SOMETHING.x.y.z = {{ITEMS}}

`SOMETHING.x.y.z` will be equal to `["a", "b", "c"]` after interpolation.
Previously, this would cause an error when the settings file was parsed.

- Moved the functionality for accessing nested items via dotted names
from `Settings` to a new class, `DottedAccessMixin`. This allows the
dotted access functionality to be reused without having to create
`Settings` objects in cases where that's not needed.
- Added a default/example `DottedAccessDict`. An existing dict can be
wrapped with this to easily get dotted access.
- Fixed tox config, which revealed a couple issues on Python 2.7, which
were fixed (`raise from` and `super()` without args).

- Add support for Django 1.10. Note in the README that it's supported, install
it by default in development, and add it to tox.ini.
- Start supporting Python 3.6 and Django 1.11. This is provisional for the time
being since Django 1.11 is still in alpha.
- Improve some internal bits in the `Settings` class.
- Improve tox config; test all Django versions for each Python version in order.