Use dashboard image from master branch in tests

So that the omar/report-download branch can be deleted

Fix dashboard report image download

Restore functionality for showing choice tips on click

Problem Builder: Add instance-wide option to hide global feedback and results for Long Answer blocks

- More neutral default for "get_option"
- Separate integration tests for checking persistence behavior

feedback should be shown when student returns to block.

The new setting is called "pb_hide_feedback_if_attempts_remain".

When set to True, Problem Builder blocks will not show global feedback
messages (as long as one or more attempts remain), and will hide
results (correct/incorrect icons) for Long Answer blocks.

OC-1387 Always show tooltips feedback if tips are present.

Ensure default theme is used if theme has not been customized

Problem Builder: Add instance-wide option to hide previous answers for MCQs

- Refactor: Take advantage of mixins from xblock-utils accessing xblock settings.

- Fix existing tests.
- Add unit tests for code that deals with instance-wide options.
- Add integration test for scenario where previous answers for MCQs are configured to be hidden.

MCQs are shown when users revisit them.

blocks works in both Apros and the LMS.

Fix exponential rerendering after hitting next button too many times.

Bump version.

Implement Django Migrations

Create Django migrations, deprecate South.

Step Builder: Explain review links to users

Fix flaky tests

And remove .travis.yml file.

Copied from https://github.com/django/django/pull/3121/files#diff-f6d1c75ec606389da5af6558bf57f171

See code comment for more info. Unfortunately, I wasn't able
to find anything better than time.sleep().