v0.2

Add some tests and documentation of the internals (@talex5 #9).
Bridge Eio and Lwt cancellation (@talex5 #8).
- Cancelling a run_lwt Fiber cancels the Lwt promise.
- Cancelling a run_eio promise cancels the Eio fiber.
Add run_lwt for consistency with run_eio and Async_eio (@talex5 #8).
Add Lwt_eio.Token.t token to ensure library is initialised (@talex5 #5). with_event_loop now passes a Lwt_eio.Token.t to its callback.
Update to Eio 0.2 (@talex5 #4). Eio 0.2 renamed "fibre" to "fiber". This fixes the deprecation warning.

v0.1