Epsilons

Adds optional epsilon to pointOnLine, pointOnPolygon, and pointWithLine. Fixes #19.

Adds polygonScaleX and polygonScaleY

See #17

lineIntersectsline improvement

Ensure lineIntersectsLine returns true if line share common endpoint. See #10.

v2.2.0

Allow for polygonArea to return signed areas

v2.0.2

Ignore points with invalid values (null, undefined, NaN, Infinity) in polygonBounds.