Added Item, Container, and Order resources. Fixed and added a lot of tests.
Allow setting custom timeouts
Added carrier option to address verification
Enable `Shipment#lowest_rate` to handle nil argument
Ignore Gemfile.lock when developing a gem

ref http://yehudakatz.com/2010/12/16/clarifying-the-roles-of-the-gemspec-and-gemfile/
Merge pull request #16 from deeeki/ignore_gemfile_lock

Ignore Gemfile.lock when developing a gem
Merge pull request #15 from deeeki/lowest_rate_with_nil

Enable `Shipment#lowest_rate` to handle nil argument
Merge pull request #14 from laurynas/master

Allow setting custom timeouts
allow client-wide http configuration