Fixed Devices with spaces in name & leverage jsontool

Altered the listing and pushing functions to leverage jsontool to parse returned JSON from the PushBullet API.

Current logic assumes that the returned JSON is "prettified", but this could potentially change. Using jsontool, this allows access to the JSON data without grep workarounds and prevents problems if PushBullet decided to "unpretty" their API.

These commits also help fix a problem with device names that have a space in them (e.g. "Galaxy Nexus", "Nexus 7").