Adding ability to filter by area
Extending area selection to all methods
Full list of areas

[does it make sense to have this as its own file, or should we just send people to the source file that enumerates them?]
Full list of areas

[does it make sense to have this, or should we just point people to lookups.py ?]
Clarified which methods can specify property type
Documenting area filtering
switch from .md to .txt

renders this file more legibly with minimal effort
fix missing comma
Update README.md
remove duplicate def of AREAS

now refers back to lookups.py instead, where that list is already defined.
bugfix: get_all_listings can filter by area now

previous version wrongly passed the global AREAS on in the call to get_new_listings instead of the value of areas it was given.
Avoids gratuitous looping through areas list

If the areas argument is not provided to get_all_listings, get_all_active_mls_numbers or get_new_listings, they simply don't filter by area, as opposed to the previous version which filtered by every area in turn.
refactor pull request a bit, extract criteria thingy
filter by city too
add support for filtering by cities too
extract criteria
update readme