Fixed Mesos version in getting started doc.
Fixed Mesos version in getting started doc.

Review: https://reviews.apache.org/r/36912

chhsia0/mesos,jpeach/mesos,Aman-Jain-14/customizedMesos,Aman-Jain-14/customizedMesos,asamerh4/mesos,Gilbert88/mesos,verizonlabs/mesos,yuquanshan/customizedMesos,dforsyth/mesos,zmalik/mesos,andschwa/mesos,asamerh4/mesos,reneploetz/mesos,verizonlabs/mesos,jpeach/mesos,reneploetz/mesos,dforsyth/mesos,verizonlabs/mesos,reneploetz/mesos,zmalik/mesos,verizonlabs/mesos,neilconway/mesos,asamerh4/mesos,verizonlabs/mesos,asamerh4/mesos,reneploetz/mesos,gsantovena/mesos,chhsia0/mesos,yuquanshan/customizedMesos,jpeach/mesos,asamerh4/mesos,kaysoky/mesos,zmalik/mesos,Gilbert88/mesos,zmalik/mesos,craimbert/mesos,andschwa/mesos,reneploetz/mesos,yuquanshan/customizedMesos,craimbert/mesos,chhsia0/mesos,jpeach/mesos,yuquanshan/customizedMesos,craimbert/mesos,chhsia0/mesos,kaysoky/mesos,kaysoky/mesos,chhsia0/mesos,andschwa/mesos,jpeach/mesos,abudnik/mesos,neilconway/mesos,asamerh4/mesos,gsantovena/mesos,Aman-Jain-14/customizedMesos,craimbert/mesos,craimbert/mesos,kaysoky/mesos,neilconway/mesos,dforsyth/mesos,abudnik/mesos,Aman-Jain-14/customizedMesos,chhsia0/mesos,abudnik/mesos,neilconway/mesos,Gilbert88/mesos,jpeach/mesos,gsantovena/mesos,yuquanshan/customizedMesos,Gilbert88/mesos,Gilbert88/mesos,Gilbert88/mesos,andschwa/mesos,craimbert/mesos,dforsyth/mesos,neilconway/mesos,dforsyth/mesos,yuquanshan/customizedMesos,Aman-Jain-14/customizedMesos,yuquanshan/customizedMesos,zmalik/mesos,andschwa/mesos,Aman-Jain-14/customizedMesos,dforsyth/mesos,gsantovena/mesos,craimbert/mesos,kaysoky/mesos,reneploetz/mesos,chhsia0/mesos,asamerh4/mesos,zmalik/mesos,abudnik/mesos,abudnik/mesos,dforsyth/mesos,zmalik/mesos,andschwa/mesos,Gilbert88/mesos,reneploetz/mesos,Aman-Jain-14/customizedMesos,verizonlabs/mesos,verizonlabs/mesos,kaysoky/mesos,abudnik/mesos,abudnik/mesos,kaysoky/mesos,neilconway/mesos,gsantovena/mesos,andschwa/mesos,gsantovena/mesos,jpeach/mesos,gsantovena/mesos,neilconway/mesos