Gave main header more appropriate wording, and added horizontal rule to separate main features from "optional features" section.
Gave main header more appropriate wording, and added horizontal rule
to separate main features from "optional features" section.

ecs-hk/ec2-cfengine37,ecs-hk/ec2-cfengine37,ecs-hk/ec2-cfengine37,ecs-hk/ec2-cfengine37