docs: update homepage to announce 3.1
docs: update homepage to announce 3.1

Change-Id: Ide4175f48b765484f0a1bbb5be3bc56e79e97612

xorware/android_frameworks_base,xorware/android_frameworks_base,xorware/android_frameworks_base,xorware/android_frameworks_base,xorware/android_frameworks_base,xorware/android_frameworks_base