Adding tests for patches in 1.0.2

The patch was released in an emergency. This test suite confirms that
the patch release does work as intended, and used to fail on 1.0.1.

All three major cases are tested:

- Unknown PROXY subprotocol
- Garbage down the line
- Timeout during the handshake
Deduplicating some test code
Merge pull request #9 from heroku/failure-cleanup-tests

Adding tests for patches in 1.0.2