Emit text and marker change events when skipping undo

[as-cii]

Back in #255 we introduced a regression that prevented the following events from firing when calling setTextInRange with undo: 'skip':

• buffer.onDidChangeText
• buffer.onDidStopChanging
• markerLayer.onDidUpdate
• marker.onDidChange

This pull-request fixes it by calling emitMarkerChangeEvents and emitDidChangeTextEvent at the end of setTextInRange if the transact call depth is 0 and undo is 'skip'.

/cc: @nathansobo

[nathansobo]

I see, because we don't transact if we're skipping undo and so the events that typically are fired at the end of the transaction are skipped. 👍