Add documentation

[clue]

Closes#14

[clue]

Note that this also describes the cancellation feature from PR #13, so we have to wait for that PR to land first.

[jsor]

For React/Promise >= 2.2 this can be:

Timer\timeout($promise, 10.0, $loop)
->then(function ($value) {
// the operation finished within 10.0 seconds
})
->otherwise(function (Timer\TimeoutException$error) {
// the operation has failed due to a timeout
})
->otherwise(function ($error) {
// the input operation has failed due to some other error
})
;

Note that i intentionally omitted rethrowing the exception.

[clue]

Note that this also describes the cancellation feature from PR #13, so we have to wait for that PR to land first.

I've just removed this and force-pushed an update without the cancellation feature.

I'm aiming to get this in soon, while the cancellation feature may still take some time.

[clue]

Ping @jsor

[jsor]

LGTM