Increase version to 1.0.1, in preparation for PyPI release. This release
includes a fix by Jayson Vantuyl to an error code import. A proper error
is now emitted when omitting the keyfile on a PyDTLS server.
The version number is incremented to 1.0.0.
Thanks to doneir for reporting that a number of unit test were failing.
This was because two test certificates had expired. This commit replaces
these with updated certificates, along with the tool used for programmatic
certificate generation. The new certificates are set to remain valid for
approximately ten years.