message: Improve docstring on contrib summary module
diff: # See the License for the specific language governing permissions and
  # limitations under the License.
  # ==============================================================================
  +"""TensorFlow Summary API v2.
  -"""Contrib summary package.
  -
  -The operations in this package are safe to use with eager execution turned or on
  -off.
  -
  +The operations in this package are safe to use with eager execution turned on or
  +off. It has a more flexible API that allows summaries to be written directly
  +from ops to places other than event log files, rather than propagating protos
  +from @{tf.summary.merge_all} to @{tf.summary.FileWriter}.
  """
  from __future__ import absolute_import
  