title: Split tensor into training and test sets
body: <p>Let's say I've read in a textfile using a <code>TextLineReader</code>. Is there some way to split this into train and test sets in <code>Tensorflow</code>? Something like:</p>
  
  <pre><code>def read_my_file_format(filename_queue):
    reader = tf.TextLineReader()
    key, record_string = reader.read(filename_queue)
    raw_features, label = tf.decode_csv(record_string)
    features = some_processing(raw_features)
    features_train, labels_train, features_test, labels_test = tf.train_split(features,
                                                                              labels,
                                                                              frac=.1)
    return features_train, labels_train, features_test, labels_test
  </code></pre>