Add cache control header configuration

[jimlambie]

CDN requires cache control headers configurable by mime type:

For example see the Apache directive below,
add a long cache expiration for images that are not going to change

#1 Month for all your static assets
 <filesMatch ".(ico|pdf|flv|jpg|jpeg|png|gif|js|css|swf)$">
 Header set Cache-Control "max-age=2592000, public"
 </filesMatch>

[jimlambie]

Add to config:

Order of precedence: paths, mimetypes, default

headers: {
    useGzipCompression: true,
    cacheControl: {
      "default": "public, max-age=3600",
      "paths": [
        {"path/to/asset.css": "public, max-age=10800"}
      ],
      "mimetypes": [
        {"text/css": "public, max-age=86400"},
        {"text/javascript": "public, max-age=86400"},
        {"application/javascript": "public, max-age=86400"}
      ]
    }
  }