Clarified motivation and responsibilities of maintainers.
Clarified motivation and responsibilities of maintainers.

Review: https://reviews.apache.org/r/49975

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