Updated Demographics and Enrollment Mode Serializers with Defaults

Both serializers will not return 0 if a demographic or mode field value is set to None.

Defaulting to zero to avoid downstream issues with None values.

Education level returned as a string.

Added Enrollment Mode

Updated enrollment/gender endpoint to aggregate gender counts by day.

Added REST API for Grade Distribution and Sequential Open Distribution

Updated Course ID Regex and CSV filename

File names are now compatible with opaque keys.

This regex is nearly identical to the one used by LMS. The only difference is the internal capture groups have been replaced with character sets to avoid issues with the Swagger UI attempting to parse the internal capture groups and pass them along as arguments.

Updates for Travis

- Added new make target
- Updated fake data management command to accept an argument determining the amount of data to generate

Removed forum data from activity resource

We don't currently have the data. I have commented out the relevant code.

Remove deprecated setting; replace with new version.

Build on Travis and Badges

TE-476

Redirecting Status sub-paths to Root

Calls to /api/v0/status|health|authenticated are now redirected to /status|health|authenticated.

Grouping Unknown Locations More Efficiently

Grouping and Returning Unknown Locations

Enrollment-location rows without a valid ISO-3166 country code are grouped into an UNKNOWN entry returned by the API.

- Start dates are on Mondays
- Adhering to closed-open intervals

Fixed Times for Fake Activity Data

Revert "Upgraded to Django 1.7"

- Start date is now on Sunday at 00:00
- End date is now on Saturday at 23:59:59

Upgraded to Django 1.7