Vector: add required header (#126)

Closes: #125

Author: barracuda156

src/helpers/Vector.cpp

@@ -1,4 +1,5 @@
 #include "Vector.hpp"
+#include <cmath>
 
 Vector2D::Vector2D(double xx, double yy) {
     x = xx;
@@ -16,4 +17,4 @@ double Vector2D::normalize() {
     y /= max;
 
     return max;
-}
+}