Moving to running analytics tests on 16.04

This commit also switches us from coveralls to codecov.

Updated field names in course summaries.

* renamed start/end_time to start/end_date
* renamed modes to enrollment_modes

Change edx-django-release-util version.

Adds the course metadata enrollment summary endpoint.

* Refactored tests to use a variety of course IDs using ddt
* Bump versions of opaque keys and ccx libraries
* Added timeout check to see if the elasticsearch index is ready in tests (fixes flaky tests)

AN-7880 Uncomment including "posted_forum" events

Change edx-django-release-util version.

Use date instead of datetime in ModuleEngagementMetricRanges.

Change edx-django-release-util version.

Adds CSV support to the LearnerListView

* Puts pagination previous/next links in the HTTP header
* Allows the returned field list (for CSV only) to be limited by the
  'fields' query string parameter.
* Flattens CSV list fields into a comma-delimited string, instead of showing list.0,list.1..
* Upgrades djangorestframework-csv to maintain fields/heading sort order in CSV.
* Avoids duplicate-code warnings by moving the CSV response validation tests to
  a new analytics_data_api.v0.tests.views.VerifyCsvResponseMixin

Adds endpoint to download course reports

Added 10 new userprofile fields to RosterEntry

and its corresponding LearnerSerializer, and tests.

Fix: add "--run-syncdb" to the migrate Make rule

Upgrade to Django 1.9

Fixed serialization of problem part IDs and tags.

Update DRF to 3.4.6