support for style.cssText (getting and setting)

This allows you to set the style attribute as a css string rather than just by key. It parses the css string and sets the appropriate properties.

```js
div.style.cssText = "border: 1px solid #333333; padding: 10px"
```

Relevant hyperscript PR: https://github.com/dominictarr/hyperscript/pull/10

See https://developer.mozilla.org/en-US/docs/Web/API/CSSStyleDeclaration