enable css selectors for more elements against Watir

area, audio, canvas, div, h1-6, label, li, p, span, td, video

Enables css identifiers against watir by swapping out, for example, this call:

```ruby
browser.div(:css => 'section .bar') #watir does not support this
```

with this:

```ruby
browser.element(:css => 'section div.bar')
```

Smart enough to work with multiple selectors (`.bar, .baz` turns into `div.bar, div.baz`) and avoids excess tag selectors (`.bar, div.baz` turns into `div.bar, div.baz`).

Will fail if you have, for example, a comma inside your selector (`[href=,]`).