Version 1.1

- Renamed namespace from "Async" to "async":
 -- Resolves a conflict with a library used at work,
 -- Matches the 'zmq' lowercase naming convention;
- Renamed base classes:
 -- Matches 'zmq' naming schema:
 - Async::Workload -> async::workload_t
 - Async::FireAndForget -> async::dispatcher_t
 - Async::RunAndReturn -> async::worker_t
 - Async::RunAndReturnLocal -> async::static_worker_t
- Made member Work() non-const

I promise I won't rename everything again :)

Version 1.0

- Initial version.