* Ignore all types of coverage files.

  I was getting things like `.coverage.$user`.

* Refactor existing serializers.

  Some serializers had their metadata all the way at the top
  of the file in separate variables, even though no other
  serializer were using those variables.

* Put things into proper places to make it easier to read
  and change, without having to jump up and down a 1000+
  line file.

* Add new serializers and use them in viewsets.

  These are the serializers for all 4 new endpoints,
  for courses, course runs, programs, and their aggregation.

* Add new mixin for detail endpoint.

  The mixin will add `/detail` to the end of whatever viewset
  that uses it.

* Call isort on the codebase.

* Refactor serializer test code.

  This will make it x10 easier to add tests for the
  serializers we introduced in this PR.

* Add test code for serializers.

* Refactor and add tests for viewsets.

Updated travis to use the i18n-tools validate
to validate translations in pullrequests.
LEARNER-2556

updated i18n-tool to latest version

-pull atleast 1% translated languages

-added push translations make target

-removed generate merge options

-removed i18n tools commands from extract translations

-removed existing translations

-extracted translations

-new translations

-compile messages

This reverts commit 2d188348.

Added salutation field in person model, also updated
refresh course metadata command and API to map this
new field.

LEARNER-4000

Increase the course run short description override db limit to count
for foreign characters.

LEARNER-4673

[LEARNER-4061]

We weren't propagating entitlement type/price changes to existing
seat products.

LEARNER-4347

The feature has fully landed. We just want it always on now.

LEARNER-4152

In the frontend, TinyMC is removing `\n` `&nbsp` which backend wasn't causing mismatch between the counts. Now updated the backend to use `get_text(strip=True)` method which will remove these from the text.

Revert "EDUCATOR-2231 Drop the enrollment start and end date fields from publisher course runs model"

This reverts commit d5a6bea1.

When publishing, we want to give ecommerce the UUID of the course
so that it doesn't have to turn around and ask us for that same bit
of information.