Allow to set custom lookup option for Geocoder.search, Geocoder::Query.new and ActiveRecord::Base.(reverse_)geocoded_by

  Examples:

    class City < ActiveRecord::Base
      geocoded_by :address, :lookup => :nominatim
    end

    Geocoder.search("address", :lookup => :nominatim)

Use \A and \z in regular expressions to avoid newline issues. Also, do not consider any address that begins with 127 to be a loopback IP.

This addresses:
https://github.com/alexreisner/geocoder/issues/322

This allows searching by, for example, WOEID with Yahoo PlaceFinder.

Also move some lookup-related methods to Geocoder::Lookup module.