Fix textarea HTML parsing

In modifying getContent, we neglected the fact that parseAttrs wraps arrays in HTML.Attrs.  Now we wrap arrays outside of parseAttrs near the code that modifies the attributes array for textarea contents.

Needs tests
Remove Array.prototype.slice.call on a NodeList.

It breaks in IE8.
Fix Vincent’s textarea bug

Textarea would get same content as previous tag in a template, because the variable wasn’t cleared!

Needs test
Fix `parentNode` check to decide whether to call a moveElement UI hook.

IE8 sets an element's `parentNode` to an HTMLDocument at funny times
even when the element hasn't been added to the DOM (like if you add a
child to the element), so a check for falsey sometimes misleads us into
thinking that the element is in the DOM when it's not (and thus calling
a moveElement UI hook for an element that was never inserted).

The corresponding check on `removeElementWithHooks` is okay, because if
the element's parentNode is an HTMLDocument, we won't find a ui hook to
call (unless you for some reason added ui hooks to the HTMLDocument).

Fixes "ui hooks" test in IE8.
Update `canonicalizeHtml` list of DOMRange/DOMBackend element properties.

Fixes "ui hooks - nested domrange" test in IE8.
Throw errors in {{foo bar}}, foo not a function

Fix the “simpler helper” test and expand the cases where we detect that “foo” is missing or not a function (e.g. is a scalar property of the data context).
Fix Parties on IE9 by not using parentElement

Using parentElement instead of parentNode was probably a typo.  I didn’t even know there was an Element#parentElement alongside Node#parentNode in the DOM, but apparently there is, and apparently IE 9 supports it, but for some reason it doesn’t work.

The lesson is: never use parentElement on a DOM node.  Use parentNode and be done with it.
Prevent error in console when running tests
Make test-in-browser show current client test
Output results in xunit format