Slave/Agent Rename Phase I - Updated terms in the website.
Slave/Agent Rename Phase I - Updated terms in the website.

Review: https://reviews.apache.org/r/47909/

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