tell browsers they can cache can assets for a year
tell browsers they can cache can assets for a year

test plan:
* first, clear out all the cdn assets on your test
s3 bucket by running this in rails console:
Canvas::CDN::S3Uploader.new.bucket.objects.with_prefix('dist').delete_all
* compile_assets
* run bundle exec rake canvas:cdn:upload_to_s3
* access canvas in your browser
* on js/css/image assets (like common-xxxxx.js)
  you should see a "max age 1 year" header

Change-Id: I7847e614a0e3066686bda32f8854263f78cc168f
Reviewed-on: https://gerrit.instructure.com/59184
Tested-by: Jenkins
Reviewed-by: Cody Cutrer <c4fe2b1d90ef8f2548c8aeabfa633434316f0305@instructure.com>
QA-Review: Jeremy Putnam <b030d6d6f199f844ec424882be473c2ab9adc93b@instructure.com>
Product-Review: Ryan Shaw <ea3cd978650417470535f3a4725b6b5042a6ab59@instructure.com>

snehakachroo1/LSI_replica,efrj/canvas-lms,roxolan/canvas-lms,kyroskoh/canvas-lms,instructure/canvas-lms,fronteerio/canvas-lms,whalejasmine/canvas-lms,efrj/canvas-lms,SwinburneOnline/canvas-lms,venturehive/canvas-lms,grahamb/canvas-lms,grahamb/canvas-lms,jay3126/canvas-lms,greyhwndz/canvas-lms,jay3126/canvas-lms,snehakachroo1/LSI_replica,utkarshx/canvas-lms,instructure/canvas-lms,fronteerio/canvas-lms,utkarshx/canvas-lms,skmezanul/canvas-lms,sfu/canvas-lms,djbender/canvas-lms,instructure/canvas-lms,greyhwndz/canvas-lms,narigone/canvas,greyhwndz/canvas-lms,sdeleon28/canvas-lms,tgroshon/canvas-lms,antoniuslin/canvas-lms,skmezanul/canvas-lms,narigone/canvas,leftplusrightllc/canvas-lms,roxolan/canvas-lms,fronteerio/canvas-lms,matematikk-mooc/canvas-lms,redconfetti/canvas-lms,sfu/canvas-lms,whalejasmine/canvas-lms,instructure/canvas-lms,grahamb/canvas-lms,snehakachroo1/LSI_replica,matematikk-mooc/canvas-lms,greyhwndz/canvas-lms,leftplusrightllc/canvas-lms,sfu/canvas-lms,djbender/canvas-lms,juoni/canvas-lms,tgroshon/canvas-lms,SwinburneOnline/canvas-lms,juoni/canvas-lms,djbender/canvas-lms,utkarshx/canvas-lms,tgroshon/canvas-lms,leftplusrightllc/canvas-lms,sfu/canvas-lms,skmezanul/canvas-lms,antoniuslin/canvas-lms,instructure/canvas-lms,fronteerio/canvas-lms,antoniuslin/canvas-lms,narigone/canvas,sdeleon28/canvas-lms,jay3126/canvas-lms,roxolan/canvas-lms,roxolan/canvas-lms,whalejasmine/canvas-lms,whalejasmine/canvas-lms,dgynn/canvas-lms,SwinburneOnline/canvas-lms,skmezanul/canvas-lms,tgroshon/canvas-lms,venturehive/canvas-lms,antoniuslin/canvas-lms,leftplusrightllc/canvas-lms,SwinburneOnline/canvas-lms,matematikk-mooc/canvas-lms,djbender/canvas-lms,instructure/canvas-lms,sfu/canvas-lms,venturehive/canvas-lms,dgynn/canvas-lms,dgynn/canvas-lms,kyroskoh/canvas-lms,AndranikMarkosyan/lms,redconfetti/canvas-lms,instructure/canvas-lms,sfu/canvas-lms,grahamb/canvas-lms,redconfetti/canvas-lms,snehakachroo1/LSI_replica,juoni/canvas-lms,jay3126/canvas-lms,narigone/canvas,kyroskoh/canvas-lms,utkarshx/canvas-lms,HotChalk/canvas-lms,AndranikMarkosyan/lms,AndranikMarkosyan/lms,efrj/canvas-lms,juoni/canvas-lms,HotChalk/canvas-lms,HotChalk/canvas-lms,matematikk-mooc/canvas-lms,sfu/canvas-lms,HotChalk/canvas-lms,kyroskoh/canvas-lms,redconfetti/canvas-lms,AndranikMarkosyan/lms,sdeleon28/canvas-lms,dgynn/canvas-lms,venturehive/canvas-lms,grahamb/canvas-lms,efrj/canvas-lms,sdeleon28/canvas-lms