Renamed service_discovery package to service package.
Discoverer is responsible for creating and then updating Devices using a DeviceMap
Discoverer maps a devices metadata to its name.
Renamed discoverer to browser.
Cleaned up some of the inconsitencies in browser.go
Added more info to the Device struct.
Comments.
Browser belongs to airplay package.
Refactored the project so that browser and device are a part of the airplay package.  Removed unneeded stuff.