Add web_api.location.ItemPostLocator

With a known list of buildings (copied from
floorplans.mit.edu/cgi-bin-db-any/wdbanyscript.asp?Report=bl&Item=OWNED),
ItemPostLocator returns a dictionary with 'lat' and 'lon' keys for a given
item, or None if it can't locate that item.
Merge pull request #7 from alexkonradi/building-locations

Add web_api.location.ItemPostLocator