Update `CHANGELOG.md`
Compress cache manifest files (.appcache/manifest)

* Cache manifest files are basically text files, therefore,
  they compress quite nicely.

* Browsers that have support for the application cache mechanism
  don't seem to encounter any problems when the cache manifest
  files are being served compressed.

See also: http://www.whatwg.org/specs/web-apps/current-work/multipage/offline.html
v2.5.0