Potential inconsistency when handling multiple mutations

[MarcusLongmuir]

When running a NetworkedDOM document without the monkeypatching applied in JSDOMRunner, there is a possibility that the diffs between states that are sent to a connected client are not consistent with the order of mutations and values that the document underwent.

This was originally indicated with an intrusive error message, but this (will be/was) removed in #101:

mml/packages/observable-dom/src/ObservableDOM.ts

Line 146 in d10f2a9

"More than one mutation record received. It is possible that intermediate states are incorrect.",