new piwi github username

Conflicts:
	demo/index.php
	src/Maths/Geometry/AbstractGeometricObject.php
	src/Maths/Geometry/Circle.php
	src/Maths/Geometry/Disc.php
	src/Maths/Geometry/Line.php
	src/Maths/Geometry/Quadrilateral.php
	src/Maths/Geometry/Segment.php
	src/Maths/Geometry/Triangle.php