C4.5 notebook added, C4.5 missing stopping criteria added

- C4.5 notebook added
- stopping criteria added for all same attributes

[Notebook output](http://nbviewer.ipython.org/gist/mazumdarparijat/e5fd491c7ed44253d122)
Hmm I am probably misunderstanding something but if you do `i=1` and `num_vecs==1` then the body of the loop will never be executed because `i<num_vecs` evaluates to `false` from the very first moment.