Django-crispy-forms

* Removed support for Python 2.
* Removed support for Django versions prior to 2.2.
* CSS for Column layout object in Bootstrap 4 template pack changed to 'col-md'. Default is now over ridden when another 'col' class is added to css_class.

See the [1.9.0 Milestone](https://github.com/django-crispy-forms/django-crispy-forms/milestone/9) for the full change list.

* Fixing FileField UI bug introduced with 1.8.0
* Remove is-valid css class for radio (bug introduced with 1.8.0)
* Various alignment and margin fixes for Bootstrap 4 template pack
* Documentation : using read-the-docs template, documenting how to run test suite, documenting use_custom_control help attributes

See the [1.8.1 Milestone](https://github.com/django-crispy-forms/django-crispy-forms/milestone/8?closed=1) for the full change list.

* Updated compatibility for Django 1.11, 2.1, 2.2 and 3.0 in line with Django's
supported versions policy.
* Numerous improvements to the Bootstrap 4 template pack, which may now be
considered mature.

Here are some changes that might affect custom templating you already have in
place when using Bootstrap 4 :

* Using [Custom Forms for radio and checkbox](https://www.w3schools.com/bootstrap4/bootstrap_forms_custom.asp).
You may disable this by setting `FormHelper.use_custom_control = False`.
* Using [Bootstrap 4 `"form-row"` class in place of `"row"`](https://getbootstrap.com/docs/4.3/components/forms/#form-row).
* Fixing [layout hierarchy between input and its label for checkbox and radio](https://getbootstrap.com/docs/4.0/components/forms/#checkboxes-and-radios).

<small>Links are to the relevant Bootstap 4 docs.</small>

See the [1.8.0 Milestone](https://github.com/django-crispy-forms/django-crispy-forms/milestone/7?closed=1) for the full change list.

Many thanks to all involved in bringing together a great release!

* Bugfixes following v1.7.1

See [1.7.1 Milestone](https://github.com/django-crispy-forms/django-crispy-forms/milestone/6?closed=1)
for full issue list.

* Bootstrap 4 template pack.

See [1.7.1 Milestone](https://github.com/django-crispy-forms/django-crispy-forms/milestone/5?closed=1)
for full issue list.

* Fixes compatibility with Django 2.0
* Various other fixes.

See [1.7 Milestone](https://github.com/django-crispy-forms/django-crispy-forms/milestone/4?closed=1)
for full issue list.