Lots of updates for 1.0b2
* Written against http://tools.ietf.org/html/draft-cavage-http-signatures-02
* Added "setup.py test" and tox support.
* Added sign/verify unit tests for all currently-supported algorithms.
* HeaderSigner and HeaderVerifier now share the same message-building logic.
* The HTTP method in the message is now properly lower-case.
* Resolved unit test failures.
* Updated Verifier and HeaderVerifier to handle verifying both RSA and HMAC sigs.
* Updated versioneer.
* Updated contact/author info.
* Removed stray keypair in test dir.
* Removed SSH agent support.
* Removed suport for reading keyfiles from disk as this is a huge security hole if this is used in a server framework like drf-httpsig.
Calling 1.0.  There will be other versions for other fixes. :)