[css-transitions] Updates to css-transitions ED

I've recently completed a number of edits to the CSS Transitions
Editor's Draft: http://dev.w3.org/csswg/css-transitions/

The changes are described in the changes section:
http://dev.w3.org/csswg/css-transitions/#changes
the most substantive of which are:

  * Define the model for starting of transitions and their
    interaction with other animations more precisely:
    
    *   Define the before-change style and after-change style used
        for the style comparison, using the new concept of a style
        change event.

    *   Define that a CSS transition for a property does not affect
        computed style when a CSS Animation for the same property is
        running, but that the transition is still running in terms
        of APIs.

    *   Add a note pointing out that the above definitions imply
        that transitions can start simultaneously, from the same
        change, on ancestors and descendants.

    *   Define that CSS transitions participate in CSS's cascading
        and inheritance model 
    
  * Change the rules for automatic reversing of transitions to
    shorten the duration (and negative delay) based on the portion
    of the value space traversed instead of reversing and jumping
    into the middle of the timing function. 

(For links to the working group resolutions for these, see the
spec's changelog.)

I'd appreciate review of these changes.

I also think these changes are substantive enough to be worth
publishing another working draft of Transitions to the TR page.
(There are relatively few changes to Animations, so I tend to think
it's not worth publishing at this point.)


After this, I need to go through the mailing list archives and
bugzilla to look for any other issues that I feel need to be
addressed before last call (i.e., need to be addressed in this
level), fix a few (recently added, as part of the above edits)
issues within the body text of the spec, and hopefully move both
Transitions and Animations to last call relatively soon.  But I'd
like to publish a new WD of Transitions to get wider review of these
changes before that point.

-David

-- 
𝄞   L. David Baron                         http://dbaron.org/   𝄂
𝄢   Mozilla                          https://www.mozilla.org/   𝄂
             Before I built a wall I'd ask to know
             What I was walling in or walling out,
             And to whom I was like to give offense.
               - Robert Frost, Mending Wall (1914)