Patch broken expand/stringify spec

Bindings no longer modify the syntax tree, treating it as immutable.
Montage no longer depends on the old behavior because it no longer
reserializes objects.
Unroll cancels and swaps

No longer using Function.noop but using undefined functions instead and
checking before calling.

For swapping on non-observed arrays, using unrolled swap that does not
dispatch changes and works for arrays of any size without calling out to
splice or returning a garbage array.
Update Collections dependency
Update change log
0.2.18