Optimize several parts, to reduce minified version; gives a savings of
242 bytes.
Instead of using a coffee 'for' loop to iterate over the collection in
each-*, use a global callback to do the looping.  This will global
function will eventually check the adapter for an overridden version.
The iterate processor now passes the item index to the callback.
Allow for iterate to be overridden thru the adapter.
Add support for each-* creating an {name}_index iteration count;
this is 0-based.  If each-* happens to be given an object, then _index
will contain the key.
Abstract out the attribute value expression parser.
Add support for constant-text expressions.  This new advanced parser
activates when it detects {{}} in the attribute value.  This can be
useful when building up values with variables interspersed with
constants.  An example is
href="/path/to/images/{{order.orderId}}/{{order.overlay}}.png"

This correctly handles bind/unbind, and updates to the possibly many
internal variables.