Add Accepted, Bad Gateway and Service Unavailable response builders.
Add {Required,Optional}RequestBody readers.
Merge pull request #80 from BenWhitehead/response-builders

Add Accepted, Bad Gateway and Service Unavailable response builders.
Update based on code review.

* Update readers to directly extend RequestReader for easier use.
* Update readers to minimize code duplication
* Cleanup a few stylistic issues
Add BodyNotFound exception

Update comment for body readers.
Update contributor name.
Clean up some minor nitpick items.
Fix expected exceptions
Merge pull request #81 from BenWhitehead/request-body-readers

Add {Required,Optional}RequestBody readers.
Monir cleanup