Merge pull request #7 from pysal/bucket

Very cool.  It was a mapping issue - index passed vs. the index that we want to see?
example with global shapes and bboxes
- vectorized bf
- should be easier to parallelize
- not fully implemented yet but:

In [17]: run contiguity_decomp_bf.py
[0, 1, 2, 3]
Sequential:  237.146250963
importing combinations from itertools on engine(s)
Parallel:  68.2657179832
importing numpy on engine(s)
Parallel vectorized:  2.08636283875
Serial vectorized:  3.79399108887