Shift most of scrapers/utils.py to SayIt
Change existing scrapers to use helper classes from SayIt.

I've checked that these all function, except for the Charles Taylor
one - www.sc-sl.org is currently down.

For now, let's leave out the philadelphia scraper, which is going to disappear
from sayit.mysociety.org altogether.
Remove the philadelphia scraper.

This will resurface shortly in its own repository.