Use 2.0 by default
Implement Bunny::Concurrent::ContinuationQueue#poll
Use platform-specific continuation here, too
Use time-bound continuations

If a network loop exception causes "main" session thread to never
receive a response, continuation will simply time out and raise
Timeout::Error now, which can be handled.

We do not start automatic recovery here for two reasons:

 * It will be started in the network activity loop anyway
 * It may do more damage than good

Kicking off network recovery manually is a matter of calling
`Bunny::Session#handle_network_failure`.

The main benefit of this implementation is that it will never
block the main app/session thread forever, and it is really
efficient on JRuby thanks to a j.u.c. blocking queue.

Fixes #112.
Change log update
Log auth failures as errors
Move this require under the platform guard
Bump session continuation timeout again

To make MRI happy on stress tests
Java interop, how does it work
Remove a painful test that does not make much sense

If you choose to use Bunny in single-threaded mode, you
probably won't open channels in other threads heavily.
Increase continuation timeout for this stress test
Actually raise