Choose an even more portable CSS property to test @imports.

Colors were showing up as rgb(a, b, c) in some browsers and as #aabbcc in
others.
Explicitly make {$regexp: "foo", $options: "garbage"} throw.

This check was explicitly in the old selector compiler but the rewrite dropped
it. The `new RegExp("foo", "garbage")` throws on most browsers but not on old
WebKit.
Added fix, workaround handlebars issue and added tests
Use regexp instead of isNaN for detecting integers.
Move tests from handlebars to templating, as they depend on templates. Also, extend to test a few more types.
Review from Geoff
Merge branch 'pr-651' into devel