    }
   ],
   "metadata": {
    "kernelspec": {
     "display_name": "Python 2",
     "language": "python",
     "name": "python2"
    },
    "language_info": {
     "codemirror_mode": {
 
</s> remove    "name": "python2"
 </s> add    "name": "python3" </s> remove     "version": 2
 </s> add     "version": 3 </s> remove    "version": "3.4.3"
 </s> add    "version": "3.5.0" </s> remove    "pygments_lexer": "ipython2",
   "version": "2.7.10"
 </s> add    "pygments_lexer": "ipython3",
   "version": "3.5.0"
   "display_name": "Python 3",
    }
   ],
   "metadata": {
    "kernelspec": {
   "display_name": "Python 3",
     "language": "python",
     "name": "python2"
    },
    "language_info": {
     "codemirror_mode": {
keep keep keep keep replace keep keep keep keep keep
 Polish delete mid node challenge and solution

Update edge cases and tests. 
linked_lists/delete_mid/delete_mid_challenge.ipynb