Chains (or Linking up the backend for the first page)

@codesliced I'm going to merge this up since you're conferencing, but here's some notes.

- The first enrollment page is handled by EnrollmentStart (controller and view)
- The submission of the first form is passed to Enrollment (controller), which handles the Wicked wizard flow.
- The first Wicked wizard flow is currently `student_birth_gender_and_ethnicity`, which currently has a mostly empty page
- The rest of the forms will be handled by the Enrollment controller/views via Wicked (I'll be filling these in tomorrow)
- The welcome screen is not currently wired up to the new flow. The URL is `/start`.
- The `Next` button looks a little different because it's a button rather than a link. This will be fixed tomorrow, as @andrewmaier will help me tweak any style stuff that I made look bad.
- We're definitely still on track for having this ready on time, so enjoy the conference! :8ball: