Enables Rack::Deflate for notify.js

This saves a bit of time when the user tries to load the page
that has javascript notification.
It will gzip the javascript, from my calculations the gain is
up to 27Kb.
Added max-age to notifier.js

This adds some performance to the application clients,
they won't need to download it/check for each request.
Merge pull request #552 from tscolari/master

Using Rack::Deflate and long expire dates for notifier.js
Update Changelog

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