Updated feedback service to emit events.

Backwards compatibility is maintained with the previous callback system by attaching them to events. Passing callback functions is deprecated and this will eventually be removed.
Fixed typo in documentation
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Fixed event emitting in feedback.js
New API to support sending one notification to multiple devices.

One notification object can be sent to multiple devices while only one copy of the notification is kept in memory.
* You should use the new `pushNotification` method to benefit from this. Instead of setting `Notification#device` you instead need to pass an array of device tokens to `pushNotification` as the second parameter.
* The notification object returned by errors has changed structure.
* There is now code to support multiple connections sending notifications but this isn't fully enabled yet, it may work in your environment but hasn't been tested.
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Added deprecation notice to device.js
Preparing for v1.3.0 with upgrade to q 0.9.0 with slightly different API.
Added buffers notification option
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Fix Notification.trim() for alerts with multibyte chars.