Add test_crypto to test run

- Change manual list of unit tests to automatic test discovery so that
  test_crypto runs so that we can fix it.
Add buffering to unit tests

- Add buffering to unit tests so that output is kept with the output of
  the relevant test.
Correct placement of buffer option
Update certificate and signed/encrypted messages

- Update certificate and signed/encrypted messages in test_cytpto as the
  old certificate was no longer valid.
- Add comments that show the commands used to generate the cert and
  messages.
Regenerate signed message with MIME text header
Resign XML message so tests can work

- Resign XML message using the same cert as the other message so that the
  cert is no longer out of date.
Add comment with cert expiry date
Merge pull request #16 from apel/fix_crypto_test

Fix crypto test