offline.py blocks 'responsive' config key

[t-morley]

Passing config = {'responsive': True} to offline.plot() does not have any effect.
This is because 'responsive' is not included in configkeys in _plot_html() in offline.py
Issue #907 reported other missing keys, which have now been added.
Since this could easily happen again, is there any way to automatically keep configkeys in step with the javascript?
Or could all provided keys be passed through, without filtering against configkeys, leaving it up to the user to get them right.
If there are bad consequences to passing invalid keys, so you want to keep the filtering by default, perhaps there could be an option on offline.plot() to allow the user to force keys through.

[jonmmease]

Thanks for the report @t-morley, we'll at least add in responsive key, but you're right that we should think about how to keep this from happening in the future.