Initial foreground loading for assignments pages takes excessively long

[kvablack]

This issue was first opened in manatee-android before being moved to here.

In early 2016, a change by AISD made it so that a client must make a POST request to the averages page every time before requesting an assignments page. When the scraper was updated to reflect this, the amount of time required to scrape each course's grades increased to upwards of 10-15 seconds (with only 3 cycles in the year so far), no matter the speed of the internet connection. When the grades are updating in the background, this is not much of a problem; however, if a user that is opening the app for the first time selects a course before the background task has loaded all its grades, they will be stuck with a "Loading assignments..." message for at least 10 seconds.

It is still unclear whether this slowness is an unavoidable issue with the TEAMS server of if it is something that can be improved within the scraper. Since the assignments pages always load in less than 2 seconds when accessed through a web browser, the latter seems quite possible. At the very least, some UI changes could be made in manatee-android to avoid locking the user into a static 15 second loading screen for every class when they first open the app.