speed and stability

This is the first major update of the stable version of diffDOM. The main advantages over version 1.2.0 are:
-- Speed: By using a virtual dom internally and making the diff finding mechanism more efficient, this version is about 50 times faster than version 1.2.0
-- Stability: Through extensive testing of random content over long periods of time, most of the remaining bugs have been dealt with. We have not been able to find errors in the diffing mechanism despite of having the computer spend hours on "mining" for bugs.