Require(analytics.js) to get socrates questions working again

Apparently the changes introduced by http://phabricator.khanacademy.org/D5439 caused the global Analytics variable to no longer be available in the socrates.js namespace.  So, I added this line to pul

Fixes T2048 (which also contains more details about the problem encountered)

Auditors: jace

Test Plan:
1. Launch local dev appserver
2. Visit http://127.0.0.1:8080/science/healthcare-and-medicine/the-heart/heart-introduction/v/flow-through-the-heart
3. Verify that questions can be answered, or skipped via the 3 mechanisms: submit, skip, or the X in the top-right.