have *_cfg_{pre,ap}pend pairs preint one per line in all files.
Make it possible to handle conditionals in *_cfg_{pre,ap}pend as follows:

{ 'if ($request_method != GET)' => '{ return 200; }' } ==> 'if ($request_method != GET) { return 200; }'
Change checking of value[-1,1] to key[-1,1].  This allows us to use the
following idiom which is more flexible:

{ 'if ($request_method != GET) { return 200; }' => ''}
Merge pull request #16 from hubspotdevops/add_http_additional_conf

Make *_cfg_{pre,ap}pend attributes handle conditionals reasonably well.