Using tests from test262

Hi!

Here are some changes based on the latest spec changes:

* Array operations no longer use `ToUint32`. Instead, they use [`ToLength`](http://people.mozilla.org/~jorendorff/es6-draft.html#sec-tolength) which makes much more sense.
* Uncallable predicates must throw even when the array is empty.
* Holes are skipped.

Nevermind. It should not be skipping holes. test262 got outdated. See http://wiki.ecmascript.org/doku.php?id=harmony:specification_drafts#august_24_2014_draft_rev_27