* Update frontend
Conflicts:
homeassistant/components/frontend/version.py
homeassistant/components/frontend/www_static/core.js.gz
homeassistant/components/frontend/www_static/frontend.html
homeassistant/components/frontend/www_static/frontend.html.gz
homeassistant/components/frontend/www_static/home-assistant-polymer
homeassistant/components/frontend/www_static/service_worker.js
homeassistant/components/frontend/www_static/service_worker.js.gz
* Add a default OPTIONS handler for wsgi (#2301)
When a browser makes a CORS request, it often makes a 'preflight'
options request in order to make sure the resource is valid, and that
it has the right CORS access. This adds a default OPTIONS handler for
all views. If a view needs to customize the OPTIONS handler for some
reason, it's free to, but this way CORS will work.
* Version bump to 0.21.2
* We need to allow extra keys on top level componenet config
fixes#1756
* Add comment about location of hass (fixes#1723)
* Fix for MQTT config validation on the protocol field. (#1765)
* Update frontend with weblink fix
* Fix for light service validation. (#1770)
Incorrect validation tested if passed value was a list instead of
a member of the list.
* Accept group without entities in configuration. (#1768)
* Accept group without entities in configuration.
People seem to use these as placeholders for future expansion of their
home automation dreams, and we used to accept them. We still have to
specify at least one of 'name', 'view' or 'icon' so that the group is
parsed as a dictionary.
* Also accept empty entities: key in a group.
* Additional fix for empty entities value in a group config.
* Version bump to 0.17.1
