Added Amazon AWS Android dependencies
Gave app android.permission.INTERNET
Added rudimentary usage of AWS service using Observable
Changed Observable type to ObjectListing and adjusted Log and output messages
Moved AWS stuff to new AwsService class
Collapsed unnecessary method in MainPresenterImpl
Moved AWS observer code to new inner class AwsObserver
Introducted basic intermediary ApkDatabase and created separate ObjectListingObserver
Used flatMap and converted Observable/Observer to List<String> type
Removed redundant Observer from ApkDatabase
Added ApkDatbase.findApks method with preliminary regexp for master/release apks