message: [docs] suggest using python3.6 in installation docs
diff: @@ -4,9 +4,9 @@ Installation & Configuration
  Getting Started
  ---------------
  -Superset is tested against Python ``2.7`` and Python ``3.6``.
  -Airbnb currently uses 2.7.* in production. We do not plan on supporting
  -Python ``2.6``.
  +Superset is currently tested against Python ``2.7`` and Python ``3.6``.
  +Python 3.6 is preferred. Support for Python ``<=3.6`` is planned to get
  +phased out.
  Cloud-native!
  -------------
  