Simplify bin/jsx to perform just the JSX transform.

We will continue using `bin/jsx-internal`, well, internally.

Note that this version no longer respects `@providesModule`, and it
doesn't do anything special with constants like `__DEV__`, so we can no
longer get to claim that `bin/jsx` can be used to build the core.

I'm happy about this, personally, because it demonstrates the flexibility
of Commoner.
Merge pull request #323 from benjamn/simplify-bin/jsx

Simplify bin/jsx to perform just the JSX transform
Fix backbone todo example bugs.

Fixed:
- New todo not submitting correctly (page refreshes. `preventDefault`
wasn't there.
- Old checked todo being removed will leave the checkmark on the next
todo replacing its position.
- Cannot change todo (`value`'s now a controlled field).
- `autofocus` (should be `autoFocus`, how ironic given the current
situation) on new todo input isn't working. Switched to manual
`focus()` in `componentDidMount` for now.
- More consistent breathing space between lines.
- Gutter at 80.

Added:
- Use todomvc-common base.css. The old one had to change ids to
classes. No longer necessary.
- Give `cx` a better name and move it in `Utils`.
- Trim input upon finishing edit.
- Remove todo if the new edited value is empty.
- Submit edited todo value on input blur.
- README to explain the existence of this example. Being able to
maintain a non-compilant version allows nice deviations from the
todomvc specs, such as animations, in the future.
Merge pull request #324 from chenglou/backbone-todo-ex

Fix backbone todo example bugs.
Initial build of ReactTransitionGroup

This builds `ReactTransitionGroup` with it's own copy of `React`, which
it total clownshoes. This should be technically usable, but definitely
should not be used in any production environment.
Fix bugs with CSS3 animation event in webkit

We were incorrectly sniffing the animationend event.
Cache length of NodeList when updating radios
Avoid unnecessary array allocations in dangerouslyRenderMarkup.
Supporting mounting into iframes

Sencha says that separating big components into their own iframes was important for performance:
http://www.sencha.com/blog/the-making-of-fastbook-an-html5-love-story.

Today the only thing stopping us is that events don't bubble to our events system from an iframe. This diff
looks at the owning document of the container and adds top-level listeners to it. It should not change
existing behavior and should improve our support for this.
Log unknown props only when we have a match

Logging every unknown property got very noisy when combined with use of `transferPropsTo`. I knew this would be a potential issue initially but decided it was worth it. Others disagreed and it's resulting in some confusion.

This changes the logging to ensure that we have a potential correction, so only DOMish properties should result in warnings.
Stop using comments as boundary markers in dangerouslyRenderMarkup.

Jordan warned (and StackOverflow confirmed) that IE8 doesn't respect HTML
comment nodes when setting `.innerHTML`:
http://stackoverflow.com/questions/15006001/inserting-a-comment-in-innerhtml

The virtue of the comment strategy was that the parser did all the work of
maintaining the boundaries between markup chunks, using comments as the
boundary markers.  The new strategy (of tagging the first node with a
special attribute) has a similar virtue, since the parser should preserve
that attribute only for the nodes we care about, and any rendered nodes
that do not have the attribute can be ignored (and complained about by
`console.error`).