makes the sequence nav more semantic and replaces js hover with css

Fix missing `global_context` problem

This problem was introduced in 232e758c
and caused the check answer button to not functioning.

Multiple Choice support. Outstanding issues: 
* Cleanup of the way names are handled
* Figure out why $.ajax needs a stringify
* I'd prefer to keep both input types and response types as classes. This is necessary for richer, AJAXy interactions.