API is runnable now. Errors have not been set up, yet.
Added error responses and fixed response structure.
User.java - added a "registrationId" variable for storing the registrationId of a user's phone for sending push notifications
AwsDao.java - added an authenticateUser() and getRegistrationIds() call. Authenticate does a simple lookup of a user based on the phoneId given. GetRegistrationIds grabs all the registrationIds for the given list of phoneIds.
shout.comment.CreateHandler.java - added a call to the GoogleAPIClient for sending push notifications when a comment has been made
user.AuthenticateHandler.java - refactored so a user is not created, but searched for
user.CreateHandler.java - creates a User based on the given information from the API request. Will also perform an update
servlets.ShouterService.java - added a filter for user/create calls
ApiConstants.java - added a registrationId constant
GoogleAPIClient - handles calls to the Google Cloud Messaging API so that push notifications are sent when a shout is commented on.