title: how to implement tensorflow's next_batch for own data
body: <p>In the <a href="https://www.tensorflow.org/versions/r0.10/tutorials/mnist/beginners/index.html" rel="noreferrer">tensorflow MNIST tutorial</a> the <code>mnist.train.next_batch(100)</code> function comes very handy. I am now trying to implement a simple classification myself. I have my training data in a numpy array. How could I implement a similar function for my own data to give me the next batch?</p>
  
  <pre><code>sess = tf.InteractiveSession()
  tf.global_variables_initializer().run()
  Xtr, Ytr = loadData()
  for it in range(1000):
      batch_x = Xtr.next_batch(100)
      batch_y = Ytr.next_batch(100)
  </code></pre>