Updated RTree Implementation

I’ve updated my Java R-Tree implementation on github. ┬áThese changes fix a couple of bugs:

  1. Ensure that the bounding boxes are tightened properly when nodes split.
  2. Correctly calculate new dimensions in tighten()
  3. Ensure that a non-leaf root node always has at least two elements.
  4. Added implementation of QuadraticPickSeeds, QuadraticPickNext.

Also updated the test suite.  There are no known bugs in the current implementation; please get in touch if you find any problems.