Revert pa11ycrawler back to 1.3.0

Merging rc/2016-08-31 into master

Update to latest `django-debug-toolbar`

Release Candidate rc/2016-08-30

DOC-2546: Remove refs to Hangouts; fix RTD URLs

AC-570 courseware search contrast enhancement

Current Grade Rest API implementation

pa11ycrawler 1.4.0

Also make sure we set the recommended settings according to
<https://django-debug-toolbar.readthedocs.io/en/stable/installation.html#explicit-setup>

Improve logging for email sending while registering.

Better instructions about who to ping for requirements changes

Deserialize BlockRecord.locator into a real BlockUsageLocator

Fixed Shift-Tab on menu and ARIA roles, groups

Fix discussion color contrast and remove gradients

TNL-5163

Fix spelling of permission.

Allow for site override of EDITABLE_SHORT_DESCRIPTION setting

We already have logic to serialize BUL objects to string on save,
but the corresponding deserialization logic was missing.

pa11ycrawler 1.3.0

Merge pull request #13314 from edx/tasawer/bugfix/ecom-5301-hyperlink-fixed-to-be-accessed-with-keyboard

Heperlink changed to button to be accessed with keyboard users

Adjust safe templates thresholds.

Fix typo in class name, remove incorrect class.

ECOM-5301

Fix TNL-5249: inconsistent state in discussions UI

Fix platform API documentation build

Fix the edx-documentation link

AC-566 fixing contrast for copyright

Fixed import failures that were preventing the platform API documentation from building. The problem is that the doc building environment doesn't need to install all the Python modules that the platform software does, but when Sphinx tries to import select modules so that it can use autoclass to publish docstrings it tries to import all the modules that are imported by those modules, recursively. I mocked the missing modules.