Fix #116

[dfreeman]

Prior to this, we always synthesized a class attribute at the very end of an element's attributes, so

<div class="foo" local-class="bar" ...attributes>

Would become:

<div ...attributes class="foo {{local-class 'bar' from='xxxxx'}}">

But the collision behavior with splattributes is weird when the base values are specified after ...attributes, so we switch to putting the class at the beginning.