[addons] Renamed update() directives to commands
Make EventPluginUtils clear dispatchIDs and dispatchListeners

The other dispatch utils clear these out and I found a bug where they weren't being cleared out.
I'm thinking this should probably be done in the `SyntheticEvent` constructor but at least this way it's consistent. Also, I know no one else uses `executeDispatchesInOrderStopAtTrue` except the `ResponderEventPlugin`.
Carry ajax error checking from step #13 forward to other ajax steps

The following steps also have an ajax function, but the 'error:' param
is gone after #13:
#14
#17
#19
#20
This may be superfluous, but it helped me find an error with something I
was doing - Namely, in my .json file, I had single line javascript
comments ("//") that I copied from the tutorial. I couldn't find the
issue on later steps, but was able to see my issue when the error
handler complained about an unexpected "/" in my file in step #13.
[Docs] Rendering null/false and getDOMNode.
Update tutorial.md
Restore CSSTransitionGroup tests

Not sure what happened here.

Test Plan: grunt test
Merge pull request #1324 from jordwalke/executeDispatchesInOrder

Make EventPluginUtils clear dispatchIDs and dispatchListeners
Merge pull request #1405 from spicyj/css-tests

Restore CSSTransitionGroup tests
Make code spacing more consistent

I'm a little surprised we don't have lint rules for this.
Merge pull request #1284 from plievone/directives-2-commands

[addons] Renamed update() directives to commands
Merge pull request #1386 from georgesisco/master

In the tutorial, carry ajax error checking from step 13 forward to other ajax steps
Merge pull request #1384 from chenglou/render-docs

[Docs] Rendering null/false and getDOMNode
Merge pull request #1403 from spicyj/keyword-spacing

Make code spacing more consistent
Drastically improve test performance