Remove the findDistance() stuff.

It was not well thought out, was over complicating
things, and producing inaccurate results. Easier to just
go ahead and toss them in as an insertion and deletion,
and then match up matches later.
isSame() tweaks, better subdiff, and match methods up

This should have been 3 separate commits but the earlier
 commits didn't go through for some reason. The isSame
 stuff is fairly minor, but the NodeDiff and
 SequenceMatcher changes bring major improvements to
 the results.
Deprecating getValueNode for getValue

Just making these two consistent with ReturnNode, and
the style as it exists in the remainder of the code.
Merge branch 'break-and-return' into node_diff
Refactors NodeDiff and improves the Documentation