Ember splat attributes support

[chriseppstein]

The rewriter will put the class attribute on the component invocation side, if the component is a css-blocks component, we should merge the invocations that have block styles with that component's analysis so conflict detection and declaration optimization work correctly.

[chriseppstein]

Note: that block styles cannot straddle the splat. they must all be on one side or the other. The rewriter should ensure the rewritten class attribute is on the same side as those.

[chriseppstein]

Also: Block styles after the splat seem to be ignored.