Use new latest value when gathering College Scorecard API data

[higs4281]

The College Scorecard API now offers a latest parameter to fetch
the most recent data available, which is a big improvement over
the former guessing game.

This allows us to ditch the former requirement of specifying
new values for API_year and Salary_year via the Django admin.

Changes in /data_sources/ and /fixtures/ are reference files
for data provenance.

Testing

You can use the standalone setup to run the script against a single school.
You will need an API key from the Dept. of Education for the command to succeed.

Standalone setup

Check out this branch and run the standalone setup script. This takes about 3 minutes.

./standalone_setup.sh

Fire up runserver and call up the API values for a single school. It helps to use a json viewing plugin for your browser, such as Chrome's JSONView.

unset DJANGO_SETTINGS_MODULE
./manage.py runserver

• Check the pre-script API response for the University of Kansas:
  http://localhost:8000/paying-for-college2/understanding-your-financial-aid-offer/api/school/155317/
• Open another tab and hit the same API endpoint so you can compare them after the script runs.
• Run the script for a single school:

ED_API_KEY=[KEY] ./manage.py update_via_api --school_id 155317

• You should get an echo indicating the University of Kansas was updated. You can confirm this in the API responses.
• Refresh one of the API tabs, then flip between tabs to compare. You should see updated values for
  • gradRate
  • medianMonthlyDebt
  • medianTotalDebt
  • repay3yr
  • tuitionUnderInS
  • tuitionUnderOoss

Testing a full run of the script can take a half-hour or so.

ED_API_KEY=[KEY] ./manage.py update_via_api

Note

• This version of the update script was used to process the 2018 Scorecard data.

[coveralls]

Coverage remained the same at 100.0% when pulling b340f0c on use-latest-for-api into 642bb7f on master.

[Scotchester]

Testing instructions work as expected!