Vertex now uses true division instead of casting RHS to float

- updated tests

test/vertex.py

@@ -1,6 +1,6 @@
 import unittest
 
-from surf.geometry import Vertex, cross
+from surf.geometry import Vertex
 
 
 class TestVertexOperations(unittest.TestCase):
@@ -30,6 +30,14 @@ class TestVertexOperations(unittest.TestCase):
         v2 = self.v1 / 2.0
         self.assertEqual(v1, v2)
 
+    def test_inappropriate_division(self):
+        with self.assertRaises(TypeError):
+            self.v1 / self.v2
+        with self.assertRaises(TypeError):
+            1.0 / self.v1
+        with self.assertRaises(TypeError):
+            self.v1 / 'asdf'
+
     def test_multiply(self):
         self.assertEqual(type(self.v1 * 2), Vertex)
         self.assertEqual(type(self.v1 * self.v1), Vertex)
@@ -37,7 +45,6 @@ class TestVertexOperations(unittest.TestCase):
         self.assertEqual(self.v1 * self.v1, Vertex(0, 0, 0))
         self.assertEqual(self.v1 * self.v2, Vertex(0, 0, 0))
         self.assertEqual(self.v3 * self.v4, Vertex(58, -35, -50))
-        
 
     def test_cross(self):
         i = Vertex(1, 0, 0)