Fix some links; closes gh-25

Author: WarrenWeckesser

ipython/CoupledSpringMassSystem.ipynb

@@ -16,9 +16,9 @@
       "\n",
       "This cookbook example shows how to solve a system of differential\n",
       "equations. (Other examples include the\n",
-      "[Lotka-Volterra Tutorial](LoktaVolterraTutorial), the\n",
-      "[Zombie Apocalypse](Zombie_Apocalypse_ODEINT) and the\n",
-      "[KdV example](KdV_example).)\n",
+      "[Lotka-Volterra Tutorial](LoktaVolterraTutorial.html), the\n",
+      "[Zombie Apocalypse](Zombie_Apocalypse_ODEINT.html) and the\n",
+      "[KdV example](KdV.html).)\n",
       "\n",
       "A Coupled Spring-Mass System\n",
       "----------------------------\n",