Moved documentation, and added more operators to Vertex

- added __neg__
    - added cross for Vertex * Vertex
    - added tests for these
    - moved the cube docstring up into the cube generating function

test/vertex.py

@@ -1,6 +1,6 @@
 import unittest
 
-from surf.geometry import Vertex
+from surf.geometry import Vertex, cross
 
 
 class TestVertexOperations(unittest.TestCase):
@@ -30,6 +30,36 @@ class TestVertexOperations(unittest.TestCase):
         v2 = self.v1 / 2.0
         self.assertEqual(v1, v2)
 
+    def test_multiply(self):
+        self.assertEqual(type(self.v1 * 2), Vertex)
+        self.assertEqual(type(self.v1 * self.v1), Vertex)
+        self.assertEqual(self.v1 * 2, Vertex(-2, -2, -2))
+        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)
+        j = Vertex(0, 1, 0)
+        k = Vertex(0, 0, 1)
+
+        self.assertEqual(i * j, k)
+        self.assertEqual(j * k, i)
+        self.assertEqual(k * i, j)
+
+        self.assertEqual(j * i, -k)
+        self.assertEqual(k * j, -i)
+        self.assertEqual(i * k, -j)
+
+        self.assertEqual(i * i, self.origin)
+        self.assertEqual(j * j, self.origin)
+        self.assertEqual(k * k, self.origin)
+
+    def test_negative(self):
+        self.assertEqual(-self.v1, self.v2)
+        self.assertEqual(-self.v2, self.v1)
+
 
 if __name__ == '__main__':
     unittest.main(verbosity=3)