Added a python linter to mesos-style.cpp.
Added a python linter to mesos-style.cpp.

It currently doesn't run over any files in the code base, but we will
be adding the new python CLI in a subsequent commit, which will use
this new linter.

Review: https://reviews.apache.org/r/50910/

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