Failing test for custom element namespace in IE8

This adds a failing test to the issue where custom elements that have
been registered with can.view.tag are being rendered in IE8 with a
preceding `:` because they lose their namespace. This problem does not
occur in Mustache.

The issue is likely caused by stache using cloneNode internally. There
are various issues with cloneNode that are solved by jQuery and HTML5
Shiv includes a note in their readme that they do not address the
cloneNode problem.
Fix for custom tags in IE8 using stache

This fixes a bug where custom tags used in IE8 would result in the tags
not being part of the document's namespace and therefore would be
rendered like: <:my-tag></:my-tag>.  This would also break for
non-custom tags like <header> and <footer> because stache uses
`cloneNode` which is not fixed by html5shiv.

The fix is a custom `cloneNode` for browsers with this issue that
recursively creates elements as a replacement for the browser's
cloneNode. Fixes #985
Merge pull request #985 from matthewp/stache-ie8

stache: Custom elements in IE8 contain a colon