title: Keras training progress bar on one line with epoch number
body: <p>When I use Keras to train a model with <code>model.fit()</code>, I see a progress bar that looks like this:</p>
  
  <pre><code>Epoch 1/10
  8000/8000 [==========] - 55s 7ms/step - loss: 0.9318 - acc: 0.0783 - val_loss: 0.8631 - val_acc: 0.1180
  Epoch 2/10
  8000/8000 [==========] - 55s 7ms/step - loss: 0.6587 - acc: 0.1334 - val_loss: 0.7052 - val_acc: 0.1477
  Epoch 3/10
  8000/8000 [==========] - 54s 7ms/step - loss: 0.5701 - acc: 0.1526 - val_loss: 0.6445 - val_acc: 0.1632
  </code></pre>
  
  <p>To improve readability, I would like to have the epoch number on the same line as the progress bar, like this:</p>
  
  <pre><code>Epoch 1/10: 8000/8000 [==========] - 55s 7ms/step - loss: 0.9318 - acc: 0.0783 - val_loss: 0.8631 - val_acc: 0.1180
  Epoch 2/10: 8000/8000 [==========] - 55s 7ms/step - loss: 0.6587 - acc: 0.1334 - val_loss: 0.7052 - val_acc: 0.1477
  Epoch 3/10: 8000/8000 [==========] - 54s 7ms/step - loss: 0.5701 - acc: 0.1526 - val_loss: 0.6445 - val_acc: 0.1632
  </code></pre>
  
  <p>How can I make that change? I know that Keras has callbacks that can be invoked during training, but I am not familiar with how that works.</p>