add push notification messages
add date serilizer
add date serilizer
improve logging
fix GCM category
rough implementation of registering GCM service
add rough push
add message type deserializer
Merge branches 'feature/push-notification' and 'master' of https://github.com/iveyalkin/device-radar

Conflicts:
	app/src/main/java/org/bitbucket/rocketracoons/deviceradar/network/ApiClient.java
	app/src/main/java/org/bitbucket/rocketracoons/deviceradar/screen/MainActivity.java
	app/src/main/java/org/bitbucket/rocketracoons/deviceradar/service/TrackerService.java
	app/src/main/java/org/bitbucket/rocketracoons/deviceradar/utility/Constants.java