Added a cache_hit attribute to Geocoder Result base

Fix "Mysql2::Error: Unknown column 'NaN' in 'where clause'" error

Enable ShowPostal for GeocoderCA Lookup

Merge branch 'cm-add-skip-flag' of git://github.com/cmavromoustakos/geocoder into cmavromoustakos-cm-add-skip-flag

Conflicts:
	lib/geocoder/models/mongo_base.rb
	test/mongoid_test.rb

methods to avoid creating an index by default.

Move to method-level rescue where appropriate

Avoid crashes during calculations. Geocoder.coordinates sometimes
returns nil which causes crashes in the distance and bearing calculations.
By returning a point array of [ NaN, NaN ] this distances will be also NaN
which seems to be a sensible result. If the argument to extract_coordinates
has an unexpected form, also return [ NaN, NaN ].

Change :request_headers to :http_headers (for consistency).

Conflicts:
	lib/geocoder/configuration.rb

Add support for custom HTTP request headers

Geocoder.coordinates sometimes returns nil which causes crashes in the distance
and bearing calculations. By returning a point array of [ NaN, NaN ] this
distances will be also NaN which seems to be a sensible result. If the argument
to extract_coordinates has an unexpected form, also return [ NaN, NaN ].

It's not an ideal name either, but it's short and it's slightly more
specific than "method".

Conflicts:
	lib/geocoder/configuration.rb
	lib/geocoder/stores/active_record.rb
	test/configuration_test.rb
	test/mongoid_test.rb

This addresses issue #195.

Add support for cache stores with :get and :set methods.