3.0.0-alpha1

• This package now requires PHP 5.5.
• #26: Added an event loop implementation. Also knows as the Reactor Pattern.
• Renamed Promise::error to Promise::otherwise to be consistent with
  ReactPHP and Guzzle. The error method is kept for BC but will be removed
  in a future version.
• #27: Support for Promise-based coroutines via the Sabre\Event\coroutine
  function.
• BC Break: Promises now use the EventLoop to run "then"-events in a separate
  execution context. In practise that means you need to run the event loop to
  wait for any then/otherwise callbacks to trigger.
• Promises now have a wait() method. Allowing you to make a promise
  synchronous and simply wait for a result (or exception) to happen.