Outline on Icons is too big. No differences between an icon enabled or disabled.

The outline when the icon is focused is too big and the user can't distinguish when a button icon is enabled or disabled. Adding box-shadow (same behavior for different browsers) the problem was solved.
Merge branch 'hotfix-icon-outline-too-big' of git://github.com/najor/Aloha-Editor into hotfix

Conflicts:
	build/hotfix-changelog.md