v0.8.2 - More payload content, newer dependencies

This release includes a number of small improvements. Notably:

• ApnsPayloadBuilder will now always represent alerts as dictionaries by default; if you're sending notifications to an app that depends on alerts represented as strings, you'll want to call ApnsPayloadBuilder#setPreferStringRepresentationForAlerts(boolean).
• Added payload fields to support Safari push notifications (action and url-args).
• Added the thread-id payload field
• Added configurable high/low water marks and added ClientBusyException

For a complete list of changes, please see the v0.8.2 milestone.