<abbr> dotted underling now supported by Chrome (et al.)

[jonnystening]

Chrome has recently turned on dotted underlining of <abbr> elements by default (as per Opera and Firefox' implementation) https://www.chromestatus.com/feature/4774625963671552

https://developer.mozilla.org/en/docs/Web/HTML/Element/abbr

We are currently forcing a 1px dotted bottom border under <abbr> elements, but with the recent changes users will see a double underline.

Firefox also forces this underline (Safari does not at this stage). Not sure about IE, but it's likely we're going to have to remove that 1px dotted bottom border styling (or remove the browser implementation with text-decoration: none; and force our own styling).

@justinspencer @mpcat

[jonnystening]

Just looking into this a little further... we are actually overriding the consistent underlining solution provided by Normalize.css.

nb. Normalize could do with a version bump. We're using v4.2.0 (currently v7.0.0) #348

[jonnystening]

This double underlining issue was fixed in Text Styling v2.0.1. We will keep the dotted bottom border styling as it's clearer than the dotted underline provided by browsers.