* 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.