Fix “nully attributes” test
Port tests that were using old toHTML/materialize

Some tests were actually passing because they used old code!  Not anymore.

Create Blaze.toHTML(func) and Blaze.toText(func), like Blaze.render.  Generally you should always build the HTMLjs from inside the func — and our tests should always be wrapping test content in a function literal, not passing around unrendered HTMLjs trees — but if you’re just using tags and Isolate, it doesn’t matter.