message: fix ExponentialMovingAverage documentation so that ExponentialMovingAverage.apply is evaluated within control_dependencies
diff: @@ -278,14 +278,12 @@ class ExponentialMovingAverage(object):
  # Create an ExponentialMovingAverage object
  ema = tf.train.ExponentialMovingAverage(decay=0.9999)
  - # Create the shadow variables, and add ops to maintain moving averages
  - # of var0 and var1.
  - maintain_averages_op = ema.apply([var0, var1])
  -
  - # Create an op that will update the moving averages after each training
  - # step. This is what we will use in place of the usual training op.
  with tf.control_dependencies([opt_op]):
  - training_op = tf.group(maintain_averages_op)
  + # Create the shadow variables, and add ops to maintain moving averages
  + # of var0 and var1. This also creates an op that will update the moving
  + # averages after each training step. This is what we will use in place
  + # of the usual training op.
  + training_op = ema.apply([var0, var1])
  ...train the model by running training_op...
  ```
  