Add es3ify to JSX transform

[sophiebits]

This would make #1223 easier to deal with in older browsers.

With this change,

<div class="orange" />

compiles into

React.DOM.div( {"class":"orange"} );

and this.props.class turns into this.props["class"].

[zpao]

I'm mostly certain we're not going to do this as is internally, so will probably need to shuffle around a little bit. Will talk with @jeffmo

[sophiebits]

@zpao Why not? Surely you guys don't want to worry about quoting your reserved keys for IE8.

[zpao]

as is

We may already be quoting these in a different transform internally but I don't know. Also, even if we aren't, we can't just copy-paste, visitor list set up is different.

Tangential but does es3ify do foo.class → foo["class"]?

[sophiebits]

Yeah.

[zpao]

Hmm, I guess the keywords that need to be quoted already aren't getting crushed by closure compiler so I guess that's ok.