Style dictionaries don't work

[adamlwgriffiths]

Having dicts in dicts doesn't work.
This is helpful for styling elements inline.

In [1]: from cottonmouth.tags import *

In [2]: from cottonmouth.html import *

In [3]: render([input, {'style': {'visibility': 'hidden'}}])
Out[3]: '<input style="{\'visibility\': \'hidden\'}"></input>'

Expected output:

'<input style="visibility: hidden;"></input>'

My current suggestion would be to render a dict in a dict as a CSS string.
Off the top of my head, I'm not sure where else this may be helpful or if it may cause any conflicts.