message: Fix continuous_train_and_eval docstring formatting
  First item in ordered list doesn't render properly:
  RELNOTES: n/a
diff: @@ -648,6 +648,7 @@ class Experiment(object):
  This method is intended for single machine usage.
  This differs from `train_and_evaluate` as follows:
  +
  1. The procedure will have train and evaluation in turns. The model
  will be trained for a number of steps (usually smaller than `train_steps`
  if provided) and then be evaluated. `train_and_evaluate` will train the
  