specifing apt cookbook < 2.0.0 in berksfile
use newer newrelic-ng cookbook
bump to 0.5.0 -- requires chef 11
use chef 11.6.0 in testing
removing mysql version constraint, database cookbook dependencies should cover it

this constraint + the one in the database cookbook itself seems to trigger
a bug in chef-zero's dependency resolver
remove apt cookbook version constraint in testing
remove minitest-handler
read new relic key from env vars
bump to 0.5.1