Expires Header

[LevelbossMike]

As discussed in ember-cli-deploy/ember-cli-deploy#126 we should look into expires header and if we need to to more work to improve caching.

cc @enspandi

[enspandi]

Thanks for moving the issue!

Some more information about browser caching according to developers.google.com:

• https://developers.google.com/speed/docs/insights/LeverageBrowserCaching
  "We recommend a minimum cache time of one week and preferably up to one year for static assets"
• https://developers.google.com/web/fundamentals/performance/optimizing-content-efficiency/http-caching#defining-optimal-cache-control-policy
  "Locally cached responses are used until the resource 'expires'"

And an example response on youtube.com for their javascript files:

age:15792
cache-control:public, max-age=31536000
content-encoding:gzip
content-length:28912
content-type:text/javascript; charset=UTF-8
date:Thu, 19 Mar 2015 01:59:35 GMT
expires:Fri, 18 Mar 2016 01:59:35 GMT
last-modified:Thu, 12 Mar 2015 20:40:48 GMT
server:sffe
status:200
vary:Accept-Encoding
x-content-type-options:nosniff
x-xss-protection:1; mode=block