implement basic MapQuest interface
Added basic support for geocoder.us and moved a common type into geocommon.jl

geojl now has two modules: MapQuest and GeoCoderUs.

MapQuest is an interface to MapQuest's API. It requires a key to use.

GeoCoderUs is an interface to geocoder.us's API. I haven't implemented the username/password authenticated version because I don't know how to get an account. Ihave the basic non-authenticated csv-requesting version working. It does not yet handle error messages properly (meaning at all).

GeoCommon is a module that contains a common type (SimpleLocation) shared between MapQuest and GeoCoder. I don't think I'm importing it into them correctly, but this way works at least.