Add addt’l required PHP pkgs for WP
Update spec_helper for Serverspec v2
Update H5BP Apache directives

Some formatting cleanup, but the addition of a few updated security
items & refinement of expires rules

Corresponds to:
h5bp/html5-boilerplate@d7976c3f75a88c054dd75af88e78d7ba55e08119
Pin newrelic_meetme_plugin cookbook to ~> 0.0.3
Pin newrelic cookbook to ~> 2.2
Bump to v2.4.0