Upgrading to Smack 4.1.0 API (not working yet)

SASL EXTERNAL needs back porting from Smack 4.0

Signed-off-by: Daniele Ricci <daniele.athome@gmail.com>
SASL EXTERNAL will be automatically added by Smack

Signed-off-by: Daniele Ricci <daniele.athome@gmail.com>
Use instantShutdown when needed

Signed-off-by: Daniele Ricci <daniele.athome@gmail.com>
Allow registration to GCM is Google Play services is outdated

Signed-off-by: Daniele Ricci <daniele.athome@gmail.com>
Merge branch 'master' into smack_4_1_0
Going back to master

Signed-off-by: Daniele Ricci <daniele.athome@gmail.com>
Basic checkstyle configuration (close #195)

Signed-off-by: Daniele Ricci <daniele.athome@gmail.com>
Revert "Use instantShutdown when needed"

This reverts commit 25d5ae540f5d1d27f081ea218ef9544a9316d503.
Merge branch 'master' into date_stamp