Fix notes in documentation

Use of .. note: instead of .. note:: resulting in content not
being displayed

Signed-off-by: Alexandre Marangone <alexandre.marangone@inktank.com>
Fix important in documentation

Use of .. important: instead of .. important:: resulting in content
not being displayed.

Signed-off-by: Alexandre Marangone <alexandre.marangone@inktank.com>
Fix tips in documentation

Use of .. tip: instead of .. tip:: resulting in content not
being displayed.

Signed-off-by: Alexandre Marangone <alexandre.marangone@inktank.com>