Bump version to mesos 0.28
Bump version to mesos 0.28

vivekjuneja/marathon,Caerostris/marathon,Caerostris/marathon,janisz/marathon,natemurthy/marathon,timcharper/marathon,meln1k/marathon,Caerostris/marathon,vivekjuneja/marathon,mesosphere/marathon,timcharper/marathon,natemurthy/marathon,titosand/marathon,titosand/marathon,Caerostris/marathon,janisz/marathon,guenter/marathon,yp-engineering/marathon,guenter/marathon,yp-engineering/marathon,gsantovena/marathon,gsantovena/marathon,janisz/marathon,meln1k/marathon,ss75710541/marathon,gsantovena/marathon,vivekjuneja/marathon,gsantovena/marathon,meln1k/marathon,mesosphere/marathon,Caerostris/marathon,mesosphere/marathon,mesosphere/marathon,guenter/marathon,ss75710541/marathon,timcharper/marathon,meln1k/marathon,guenter/marathon,meln1k/marathon,janisz/marathon,janisz/marathon,mesosphere/marathon,ss75710541/marathon,natemurthy/marathon,guenter/marathon,gsantovena/marathon