0.3.0:
- add support for channel bindings
- major api rework. Unfortunatly I tried to simplify the api too much
  vs gssapi and sspi. It turns out even the krb5 mechanism sometimes
  needs to exchange more than 2 tokens, specifically in the case of an
  error, in order to get a readable message extra tokens need to
  change hands. There might be other cases as well. I'm sorry for the
  churn. This rework does open the future possibility of supporting
  other mechanisms, but due to the complexity of doing that, and
  especially doing all the testing, I don't have an specific plans.

0.2.0:
- add support for flags. The first flag indicates that the supplied
  token is a negotiate token (only relevant on windows). The negotiate
  token will work IFF the negotiated mechanism is Kerberos.

0.1.1:
- merge patch to fix building when the iov feature is disabled (#1)
  thanks kiron1

0.1.0: initial release