message: docs: fix copyright current year
diff: # All configuration values have a default; values that are commented out
  # serve to show the default.
  +from datetime import datetime
  import sphinx_rtd_theme
  import sys
  import os
  @@ -61,7 +62,7 @@ master_doc = 'index'
  # General information about the project.
  project = u'envoy'
  -copyright = u'2016-2018, Envoy Project Authors'
  +copyright = u'2016-{}, Envoy Project Authors'.format(datetime.now().year)
  author = u'Envoy Project Authors'
  # The version info for the project you're documenting, acts as replacement for
  