Add support for getting the original response

Implement support for returning the original remote response
from APNS and GCM. This is especially useful for parsing the
GCM HTTP response [1] so the user can update their registration
ids.

[1] http://developer.android.com/google/gcm/http.html#response
Merge pull request #19 from dcelasun/master

Add support for getting the original response from APNS/GCM