Upgrade to latest rspec for expect syntax
Add wrapper over WebHooks

* Provide idiomatic Ruby access to posted attributes.
* Encapsulate the algorithm for validating a WebHook.
Merge pull request #17 from brewdega/basic_webhook_support

Add class to wrap webhooks.
Clean up WebHook specs.
Clean up WebHook class.
Allow WebHook to be autoloaded.
Remove references to two-argument attr method.

It has been marked as obsolete since Ruby 1.9.1.
Convert one-argument attr method calls to attr_reader for consistency.
Update the change log.