unsupport python 3.6

the ubuntu  16.04 Comes with 3.6，Downgrading is very troublesome
```
Using TensorFlow backend.
/usr/lib/python3.6/importlib/_bootstrap.py:219: RuntimeWarning: compiletime version 3.5 of module 'tensorflow.python.framework.fast_tensor_util' does not match runtime version 3.6
``