Adding dom utilities.

[mseddon]

There are a couple of questions before I PR this that are probably worth checking.

• Scala.js is currently at 0.6.5- scala-js-dom requires 0.6.7 currently. Is it okay to upgrade?
• Are you certain you don't mind scala-js-dom as a dependency for this library?

[jducoeur]

The version upgrade is certainly fine (I should do that anyway), but the dependency question is a lot more interesting. I hadn't been thinking about that (still a bit early in the morning), and it's a good point: jsext is a bit more focused on extensions to the core, rather than the dom, and the elements so far don't imply that dependency.

Humph. Much though I'd like to just say, "yeah, sure", I suspect that's a compelling argument. We should probably have a similar-but-separate grab-bag library for dom-level stuff, so that, eg, RichFuture doesn't have dom dependencies...

[mseddon]

Aha, glad I flagged that then. Perhaps adding a subproject for "org.querki" % "querki-jsext-dom" is the right way to go? Feel free to come up with a better name or method, I'm not precious.