Added Emitter::dispatch() which allows custom Event objects.
Added an async flag to observers.
Started working on async event support.
Replaced the Observer custom type with a class. Removed the CallStack custom type.
Added tests for async functionality.
Fixed remaining async problems.
Minor architecture changes. Added new ListenerOption shape.
Use custom type for params.
Fix broken tests.
Merge pull request #40 from milesj/event-async

Event Improvements
Merge branch 'master' into cleanup
Rename the @type doc to @var.
Fix the file extension for Http\Cookie.
Update copyright to 2015.
Updated PHPUnit requirement to 4.4.0.
Renamed linter to type checker. Fixed line endings.
Large list of type checker fixes.
Audited exception usage [#10]
Final polish with a few type checker fixes.