Code samples (living documentation)

Adds executable samples that act as acceptance tests and documentation.

Broken!  Need to resolve a few issues before merging:
- Sample post requires a github api key.  If you don't have it setup you'll get `expected "205 Reset Content" but received "401 Unauthorized"`.  Any sample service we can post to that doesn't require credentials?
- Recording and then validating github calls fails because of #100 (specifically Etag and Access-Control-Expose-Headers)