"Point reflection" or "point symmetry" is a basic concept in geometry where a given point, P, at a given position relative to a mid-point, Q has a corresponding point, P1, which is the same distance from Q but in the opposite direction.

## Task

Given two points P and Q, output the symmetric point of point P about Q.
Each argument is a two-element array of integers representing the point's X and Y coordinates.  Output should be in the same format, giving the X and Y coordinates of point P1.  You do not have to validate the input.

This kata was inspired by the Hackerrank challenge [Find Point](https://www.hackerrank.com/challenges/find-point)