in request to geocoding service.

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

This is in preparation for adding Maxmind as an IP lookup.

This fixes issue #244.

This requires a parameter to be accepted by the block passed to
Geocoder.configure, which means you don't need to remember that the
method is called "config"--you can call it whatever you want.
This behavior seems more standard for configuration blocks.

methods to avoid creating an index by default.

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".

For consistency with rest of code.

  - need to set `use_ssl` to true
  - also cannot use `get_response` class method for https requests
  - add a smoke_test that calls out to google for real, to make sure
    things work end to end (not using test_helper for this, because it's invasive
    and opens code under test to do it's mocking)
  - add smoke_test to default test run

Instead use an array for key, client, and channel.

This has always been the intended behavior (as shown by the README's
sample code which begins `if results.first`) but it wasn't implemented
properly. Thanks to github.com/nhippenmeyer for pointing it out.