filled out Horizontal and Vertical toEqu() methods

Horizontal.py

@@ -7,3 +7,13 @@ class Horizontal(Constraint):
         self.pt1 = pt1
         self.shape2 = shape2
         self.pt2 = pt2
+
+    def toEqu(self):
+        varrefs1 = self.shape1.toEqu(pt1)[1]
+        varrefs2 = self.shape2.toEqu(pt2)[1]
+        coeffs = []
+        for i in range(len(varrefs1)):
+            coeffs.append((1 * varrefs1[i], (self.shape1, i)))
+        for i in range(len(varrefs2)):
+            coeffs.append((-1 * varrefs2[i], (self.shape2, i))
+        return [(coeffs, 0)]

Vertical.py

@@ -7,3 +7,13 @@ class Vertical(Constraint):
         self.pt1 = pt1
         self.shape2 = shape2
         self.pt2 = pt2
+
+    def toEqu(self):
+        varrefs1 = self.shape1.toEqu(pt1)[0]
+        varrefs2 = self.shape2.toEqu(pt2)[0]
+        coeffs = []
+        for i in range(len(varrefs1)):
+            coeffs.append((1 * varrefs1[i], (self.shape1, i)))
+        for i in range(len(varrefs2)):
+            coeffs.append((-1 * varrefs2[i], (self.shape2, i))
+        return [(coeffs, 0)]