Load bootstrap CSS from the JSPM package instead of CDN.

Review Request #7907 — Created Jan. 30, 2016 and submitted — Latest diff uploaded

Information

student-sonar
master
abc18ee...

Reviewers

When I finally got CSS imports working for JSPM packages, I neglected to update
the bootstrap one. This meant that updating the version in package.json
wouldn't update things everywhere. This change switches us over to importing
the local CSS.

Verified that things still looked correct.