Added NumPy examples for Craig's presentation

Example 1: algorithm for finding the pairwise distances between all spheres in a
set. Multiple functions are defined and benchmarked to show how to use
NumPy to maximum advantage.

Example 2: the distance-finding algorithm is used for collision detection
Merge pull request #2 from cfinch/master

Added NumPy examples for Craig's presentation
Merge pull request #1 from westover/master

Merging