Allow comparison between Position and Tuple

Fixes longstanding type error.

gaphas/position.py

@@ -58,6 +58,9 @@ class Position:
     def __eq__(self, other):
         return isinstance(other, Position) and self.x == other.x and self.y == other.y
 
+    def __lt__(self, other):
+        return self[0] < other[0] and self[1] < other[1]
+
 
 class MatrixProjection(Constraint):
     def __init__(self, pos: Position, matrix: Matrix):

tests/test_position.py

@@ -17,6 +17,12 @@ def test_position(position):
     assert position[1] == pos.y
 
 
+def test_position_can_compare_with_tuple():
+    pos = Position(3, 3)
+
+    assert pos < (4, 4)
+
+
 def test_matrix_projection_exposes_variables():
     proj = MatrixProjection(Position(0, 0), Matrix())