Robust tracking of quoted and unquoted attributes

Requires https://github.com/tildeio/simple-html-tokenizer/pull/13

Instead of using the presence of a value as the identifier for a quoted state, track this in the tokenizer
@mmun so far as I see, this is only required b/c of https://github.com/tildeio/htmlbars/pull/164/files#diff-0139d41adfdc7786f8904c51d4977009R51 where a single sexpr is made the value. Should that perhaps just pass through the array with one item?

processSexpr is super odd, processing the child sexprs as a raw params value.