Add Travis configuration

Change-Id: If3b5b39c048703ff30ecdebfe82aefe4e765160a
improve state update for droplet.exited

Change-Id: I27b930c553301300a06a4944bfa11f42bee70245
expand loggin for extra instances

Change-Id: I0564533d1a2bf8c35a23ad16e4c2240b925c9ae9
less logging

log "given up on flapping instance" only once, when the crash signal
arrives. Do not log same when the missing instance is detected (as
opposed to crash signal received).

Change-Id: I7fdd11b3b82c8177900eee7e34b9a6bf2f44d480
do not cache missing_indices calculation

Change-Id: I474894d0c2d5998f68b3f883a6c57d34def35caf