Touchstone

**Bug Fixes*
* Fix a bug where the `InjectViewsMiddleware` Django middleware doesn't work
on Django Rest Framework (DRF) style ViewSets.

**New Features**
* Magic Properties now call `get_container()` at call-time:
* The Django `MagicInjectedProperties` class had some issues. It required you to
inject the `Container` instance at the time that you use the decorator which makes
writing tests very difficult -- you can't mock the container or have different
bindings in unit tests, for instance.
* Now, the bound properties call `get_container()` at the latest possible moment,
allowing you to mock your `get_container` at any point before using the
injected properties are used in your test.
* As a part of this change, we now use our own `MagicProperty` class instead
of re-using Django's `cached_property` implementation.
* This also resulted in a breaking change to the magic properties API (see below).

**Breaking Changes**
* Instead of calling (or decorating with)
`MagicInjectedProperties(container).inject_magic_properties`,
you simply now call (or decorate with) `inject_magic_properties`

* Release of v1! No major changes to the functionality.

**Bug Fixes**
* `celery` no longer required on all installs. Install with the `django_celery` extras instead.

**Improvements**
* Added python 3.8 support
* Added `isort` and `black` for code formatting

**New Feature**
* Added `touchstone_task` which is a wrapper around Celery Tasks so that you can inject
properties via class variable annotations in Celery tasks.

**Bug Fix**
* `MagicInjectedProperties` uses Django's `cached_property` which [changed](https://github.com/django/django/commit/06076999026091cf007d8ea69146340a361259f8diff-31c53995d28395e13d586859808522f6)
its behavior in version 3 so that we need to call `__set_name__` manually after adding a cached property dynamically.

**Breaking Changes**
* Renamed the `called` argument of the `bind_contextual` methods to `wants_name`
for clarity in the following situation:
python
class Thing:
def __init__(self, obj):
pass

Old API
container.bind_contextual(when=Thing, called='obj', give=MyCls)

New API which makes more intuitive sense
container.bind_contextual(when=Thing, wants_name='obj', give=MyCls)