When rendering declarations of KeyFrames disable minification

[DanielJoyce]

so that KeyFrame transformations are not broken

• Added Todo to TransformList::to_css as it needs to be refactored and we need more context.
• 4 Tests are still broken

This is mostly to get the ball rolling and to see if this fixes people's use cases around keyframes.

[DanielJoyce]

Another option is to do only whitespace minification in TransformList::to_css, and don't try and change the types.

Ideally there should be a optional minification pass added, so to_css only deals with formatting.

parse -> [ minify ] -> to_css

[DanielJoyce]

Another option would be to turn minify into an enum, expressing white_space only minification and white_space + transformation

[devongovett]

Closed by #694