JSX: Respect original spacing and newlines better

[sophiebits]

Fixes #335.

With this change, this JSX:

/** @jsx React.DOM */
var HelloMessage = React.createClass({
  render: function() {
    return <div>
      Look!
      <a href=
        "http://www.facebook.com/">Facebook
      </a>
    </div>;
  }
});

produces

/** @jsx React.DOM */
var HelloMessage = React.createClass({displayName: 'HelloMessage',
  render: function() {
    return React.DOM.div(null,
      " Look! ",
      React.DOM.a( {href:
        "http://www.facebook.com/"}, "Facebook "
      )
    );
  }
});

rather than the less-desirable

/** @jsx React.DOM */
var HelloMessage = React.createClass({displayName: 'HelloMessage',
  render: function() {
    return React.DOM.div(null,
" Look! ",      React.DOM.a( {href:"http://www.facebook.com/"}, "Facebook "      ),
    );
  }
});

[zpao]

@jeffmo, I'm going to leave this all to you. We should be able to figure out testing too now that jstransform is open and has tests.

[jeffmo]

Eyeballing this, it looks good off the top of my head; However, due to some temporary synchronization issues between the versions of these files we have checked in internally and the versions we have in github at the moment (we're behind a bit internally on react.js), I need to hold off for a day or two before I can patch this internally to run our tests against it. After that I can merge/close

Hoping to be able to do that before the end of the week though