Add Rubinius and Ruby 2.1 in README.

Add Baidu IP lookup and separate lookups into Street Address and IP
Addres lookups.

This will allow us to address long-standing char encoding issues.

Functionality to pass optional :min_radius value to 'near' searches. Only works with ActiveRecord and not Sqlite.

Change maxmind_local's sample code to another file.

In face of this known issue, .joins(...).preload(...) felt like a slightly better option (vs. :select option passed to .near()) for just the particular use case I'm up against where includes would have been useful. 

Thought it'd be worth adding to the docs, especially as preload() isn't widely demonstrated in Rails own docs.

This is too much detail for the top of the README.