title: ImportError: cannot import name normalize_data_format
body: <p>I am very new to use github. I have installed github in ubuntu 16.04, I installed python 2.7.12, tensorflow 1.9 and keras. I want to use my own custom activation and optimizer in keras RNN. I searched in web and came to know i need to install keras-contrib package to use advanced activation and custom activation function. </p>
  
  <p>So, I install the keras-contrib from github. But I don't know how to work with it and how to run the program using keras-contrib.</p>
  
  <p>But i tried with following commands</p>
  
  <pre><code> git clone https://www.github.com/keras-team/keras-contrib.git
   cd keras-contrib
   python setup.py install
  </code></pre>
  
  <p>then I tried with this following code</p>
  
  <pre><code> from keras.models import Sequential
   from keras.layers import Dense
   import numpy as np
   from keras_contrib.layers.advanced_activations import PELU
  </code></pre>
  
  <p>it showing the following error</p>
  
  <pre><code> Traceback (most recent call last):
     File "&lt;stdin&gt;", line 1, in &lt;module&gt;
     File "keras_contrib/__init__.py", line 4, in &lt;module&gt;
      from . import layers
     File "keras_contrib/layers/__init__.py", line 3, in &lt;module&gt;
      from .convolutional import *
     File "keras_contrib/layers/convolutional.py", line 15, in &lt;module&gt;
      from keras.utils.conv_utils import normalize_data_format
    ImportError: cannot import name normalize_data_format
  </code></pre>
  
  <p>Anyone please check this error and help me to sort out this error. </p>