Event Emitter for Tasks

[ahallock]

Thinking about exposing events for tasks, which could be useful for monitoring progress--using a web socket, for example.

Something like:

var task = project.tasks.queue('codename', 'payload');
task.on('end', function(msg) {
});
task.on('error', function(err) {
});
task.on('progress', function(msg) {
});