version 0.0501 - Novemver 6, 2012
 * Fix some cosmetic problems.
 * Added some parameter validation for the shipping_options method.

version 0.0500 - November 6, 2012
 * NOT backwards compatible.
 * Now works asynchronously.
 * Add SSL to web service.
 * Add shipping_options method which returns USPS postage rate calculations.

version 0.0400 - October 25, 2012
 * First public release to web service.