Edited Readme
Added question on PhysicsEngine class PairForce pointer?
minor
TODO CHECKLIST STARTED
Test
exclusive or (XOR) bitwise
Fix TODO
test
Changed Pair forces not to have Iterator and add SetPairForce function and
pointer to function that will allow us to call it once per cycle like BaseFoce
VEC: Added space for Vector class definitions
VEC: Defined assignment operator for Vector class
COL: Pulled in Jeff's pull request for the Collision Engine

Discussed Iterator, Universe, and PointMass with Wilbert, Encourage simplification
e-mailed interested students in CS2 & talke to students in CS3A.

Signed-off-by: Eli Selkin <eselkin@go.pasadena.edu>
Update PointMass.h

Wilbert's changes
Update Vectors.h

Wilbert's Changes
Update physicsengine.h

Wilbert's Changes
Update physicsengine.h
Wilbert's Changes
Update: README.md

Add my name to the readme file