#6: Create Vector2 Class

[mitchwadair]

Additions

• Adds the Vector2 class
  • this is simply an alias for Vector3, with some minor changes to the constructor and some methods, which will make it more intuitive for the 2D context that SFramework is aimed at
  • Vector2:New() will take both 1 and 2 args
  • Vector2:Forward() will error every call
  • Vector2:UnitZ() will error every call
  • Closes #6
• Update doc for new Vector2 class