[Bf-codereview] Normalize Node - Tile (issue 5576078)

[dfelinto at gmail.com]

The min and max initialization was indeed missing. it was a late night
lapse :)
No wonder my quick test didn't work and I decided to test later.

I think the NodeTwoFloats is indeed a simpler solution (if documented),
so be it.

Patch ready for commit, looking for final 'go'

http://codereview.appspot.com/5576078/