Support inline styles
Support more types of dynamic attributes.
Support => attributes.

Not elixir syntax, but it's part of the offical haml syntax. Not sure what the policy of this project is?

I want this to be able to port existing views as-is.
Add :javascript filter support.

Also groundwork for additional filter types.

Automated the parse_line so that you can't forget to add one. The test
for '%img' was missing.
Fix build_attributes return values