Updated allocator.hpp to idiomatically use the "Process wrapper" pattern.
Updated allocator.hpp to idiomatically use the "Process wrapper" pattern.

Review: https://reviews.apache.org/r/28666

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