Add Client API method to return the Class Schedule Listing page.

[aomi]

Currently, the only way to get information from this page is by invoking getCourseSections, which is an expensive call as it needs to make several round-trips to create the response. For advanced users, they can reduce the RTT by making one less call (Class Schedule Listing page) if that page is saved (and therefore the CRNs) since this page does not change very frequently.

[isaaccormack]

is this still relevant / what do you mean by this? caching the sections page in the npm package? Our current implementation (as of the latest API refactoring) gets the Class Schedule Listing page, parses it, and returns it.