Cache is now lookup-specific.

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

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

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.

Altered the Geocoder#ip_address? method to recognize IP addresses prefixed with ::ffff: as is common with webservers binding to ipv6 sockets

Signed-off-by: James McCarthy <james2mccarthy@gmail.com>

Was causing problems when installing with bundler from Git URL.

Specify path to VERSION file relative to lib/geocoder.rb.

Figures out whether query is an IP address so you don't have to.

Was ignoring non-ASCII characters. Thanks to github.com/supergivi for
reporting the bug.

...for Result instance methods mistakenly called on an array.

After further consideration, multiple results should be the default
behavior for this method. Some services only return one result (eg: any
IP-based service) but a great feature of advanced services like Yahoo
and Google is that they return an array of choices when doing a vague
search like "100 Main St" with no city, region, or country specified.

This allows us to add a method for expiring cache keys and generally
gives us more control over the cache interface.