add overflow-wrap fallback

[MattDiMu]

I've recently created a postcss-plugin to create a fallback from overflow-wrap to word-wrap and i think, it might be useful in the cssnext plugin pack:

Specification: https://drafts.csswg.org/css-text-3/#propdef-overflow-wrap
Plugin: https://www.npmjs.com/package/postcss-replace-overflow-wrap
Github-Repo: https://github.com/MattDiMu/postcss-replace-overflow-wrap
Browser Support (overflow-wrap vs word-wrap): http://caniuse.com/#feat=wordwrap

It's the first time, that I've ever contributed to cssnext, therefore I've simply worked through the Contributing.md guidelines and hopefully haven't forgotten anything.

Cheers
Matt

[MoOx]

Looks good. I understand that overflow-wrap === word-wrap. Is this a correct assumption?

[MattDiMu]

@MoOx - Yes, exactly. overflow-wrap is now simply an alias to word-wrap (having better browser support and being a bit shorter). It was renamed just like the pseudo-elements, which used to have only one double point in CSS 2.1 (e.g. :before) and finally got a second double point (e.g. ::before) to distinct them from pseudo-classes.

[MoOx]

Will probably review, merge and release at the end of the weekend.

[MoOx]

Will push as a minor release asap.

[MoOx]

I just simplified the key to "overflowWrap". Released as 2.6.0, sorry for the delay :)