handle process callback

[suruja]

Hello!

I want to use your project as a node module, and I need a callback to know when processing ends. I just add a callback to your async.series call in process function.

[GoalSmashers]

I've never had a chance to use it programatically. Would you be able to provide a test for this feature so I can merge it?

[suruja]

The callback I added to async.series is used and tested in async module itself, and the assets-packager tests suite still pass with this minor change. Do you think a new test is necessary?

[jakubpawlowicz]

It would be great to have one but there is even no skeleton for non-binary tests. Let me add it first.