Draw charts from JSON api. Fixes #24.
Decouple review charts api and rest of page. Remove aggregator from non-api views.
Add back review voting ui and link department.

* Add/style up/down voting arrows.
* Add course/prof to each others comments to provide context.
* Add review page link to department to #id link on student_browse.html
  Closes #18.
Implement comment voting. Closes #2.

* Comments sorted by upvotes - downvotes.
* Comment vote immediately reflected by colored up/down arrow.
Add detail.js to Pipeline in common.py