import now allows editing, moving people around

I also renamed some methods to make it more clear as to what it does and fixed the course enrollments per some hipchat (pending final confirmation of correctness though)
> Now that the LMS class is separate, we can write a mock object for that.
> 
> Though what I was more focused on testing was other details on canvas - like would existing assignments get changed? That's why it checks for the existing enrollment instead of just deleting them all, I wanted it to make as few changes as possible to do the update.

My main concern is finding a bug in this in the future or needing to modify it for a new use case, testing the new use case, and then having the next import run on production and fubar real users b/c all the code paths weren't accounted for by the person fixing the bug.  I'm going to accept the merge and add a task on your backlog to write unit tests around this code.  If you get blocked at any point, it will be good to have that task queued up.