env_vars as a dictionary (not list) so the it can be used for the 'environment' task property
add reqs_file variable
add htop and mercurial apt packages to common role
use deploy role
shouldn't need to set permissions again, already set when dir created
use http socket for nginx and uwsgi
add dj-cmd python package
set number of uwsgi processes to nr of cpu cores and kill each process after 5000 reqs

kill to prevent uwsgi memory leak