Function lineSegmentIntersection

lineSegmentIntersection(a, b, c, d, epsilon?): LineIntersection
An internal helper method for computing the intersection between two finite line segments. Adapted from http://paulbourke.net/geometry/pointlineplane/
Parameters
- a: Point
  The first endpoint of segment AB
- b: Point
  The second endpoint of segment AB
- c: Point
  The first endpoint of segment CD
- d: Point
  The second endpoint of segment CD
- Optional epsilon: number = 1e-8
  A small epsilon which defines a tolerance for near-equality
Returns LineIntersection
An intersection point, or null if no intersection occurred