overhaul scrapers/math_dept.py

[duck-master]

This is major overhaul of scrapers/math_dept.py. Even though I know it isn't actually being used in production, I still think it's good to make all the code as pretty and modular as possible for posterity.

More specifically, the main code in math_dept.py (all the random stuff that used to be non-indented) is now divided into:

• run(), the main entry point, which uses three other helper functions:
  • get_rows() for scraping
  • parse_subject(subject) to parse the title specifically
  • parse_row(row) to parse an individual row
• test_parse_when() as a sanity check that parse_when(when) works properly