File cleanup.
Unified the default signing algo under one setting.
Setting httpsig.sign.DEFAULT_SIGN_ALGORITHM changes it for all future classes.
Handle invalid params a little better.
Updated for Draft 3.
Added tests for HMACSHA256 and RSASHA256.
Created signature value object.
Added mock to requirements.
Added HMAC and RSA algorithms using SHA-256.
Refactor algorithms to use base classes.
Added tests for HMACSHA1.
Added algorithm class HMACSHA1.
Minor correction in docstring.
Added tests for HMACSHA512.
Added algorithm HMACSHA512.
Fixed typo in docstring.
Added tests for RSASHA1.
Created algorithm for RSASHA1.
Added tests for RSASHA512.
Added RSASHA512 algorithm.
Keep examples the same.