0.4

• Add clone method to Vector that returns a new vector with the same coordinates.
• Add angle and offset to Polygon that are used to modify the computed collision polygon (Fixes #3, Fixes #4)
  • The rotate and translate methods still exist on Polygon but they modify the original points of the polygon, wheras angle and offset do not modify the original points, and are instead applied as computed values.
• Add setPoints, setAngle, and setOffset methods to Polygon