Added initial stucts, documentation, and testing
Add core authentication code and responder utility class

Adds most core functionality for the authentication of requests.
All thas is missing is the logic to generate the string used for
signing the request based on the request headers and VanGoH struct
configuration.

Additionally added a utility class, "responder" to handle formatting
and responding with appropriate HTTP responses under different
failure conditions.
First working test based off AWS example

First test written to demonstrate the examples on the AWS HMAC
description page.

Still no support for custom headers to be included, but the rest
of signingString generation works correctly.
Move AWS-based tests into their own file, and add custom header handling

Adds handling of custom headers into the generate string used when
signing requests.  At this point, appears to match full functionality
(and a bit more) of the AWS implementation.
Cleaned up some formatting in the responder code
Introductory GoDoc