Miscellaneous `ExtEventLoop` stuff.
Miscellaneous `ExtEventLoop` stuff.

* Added `ExtEventLoop` to the event-loop readme file
* Added `ext-event` to composer suggestions
* Added messages to composer suggestions (suggest doesn't use version constraints)

reactphp/event-loop,kaduev13/event-loop,steverhoades/event-loop,clue-labs/event-loop,mkrauser/event-loop,kaduev13/event-loop,steverhoades/event-loop,mkrauser/event-loop