Mark all EDMC schools as non-Perkins

[higs4281]

This is mostly a data fixture update, but it also cleans up an IPEDS data_json loading issue and some related tests. The Department of Ed spreadsheet we used to identify Perkins schools was for 2014-2015, the latest available, but it turns out EDMC schools were denied access to Perkins loans since then. Thus this PR updates all EDMC schools to make sure their offersPerkins value is false.

Changes

• collegedata.json updated
• update_ipeds script tweaked to make sure new schools get a base data_json string to avoid key errors when calling the API.

  Testing

• run ./manage.py loaddata collegedata and then check the Art Institute of Colorado, which should show offersPerkins: false
  On build AI Colorado currently shows true

  Review

• @amymok

  Checklist

• [x] Project documentation and CHANGELOG updated

[coveralls]

Coverage increased (+0.0006%) to 99.774% when pulling 2c6582c8656d312073d0a1d0ad4bacb33f4dc59d on perkins-data into 50d8b068acfd8aa3fed27a7306c0c375c5901c94 on master.

[amymok]

Tested, it looks good!