Added test + impl of "duplicate id detection" to MessageModule
Removed GooglePushNotifications.txt file from git index
cosmetic changes related to MessageModule tests
nothing to see here...
Fixed bug related to messages being sent several times
Added new dependency (nuget package) 'Microsoft.Net.Http' in order to get the new HttpClient
added GooglePushNotifications.txt to .gitignore file
Added support for Android push notifications!