Add XML style JSX namespacing support using @jsxns docblock comment.

[percyhanna]

Adds support for using XML namespaces in JSX to refer to custom defined identifiers in a @jsxns docblock comment. Can make a namespace refer to any JS identifier.

/**
 * @jsx React.DOM
 * @jsxns {"UI": "MyApp.UI", "External": "External"}
 */

React.createClass({
  render: function() {
    return (
      <UI:Component />
    );
  }
});

Compiles to:

React.createClass({
  render: function() {
    return (
      MyApp.UI.Component(null )
    );
  }
});

Should address most of the concerns and patterns mentioned in #221.

Included some basic tests for validating namespace definition and usage.

[chenglou]

@petehunt

[percyhanna]

Also was unsure on placement of tests, I put them where I thought they were best suited, but am open to relocating them to somewhere else.

[percyhanna]

Hmm, not initially clear to me why Travis environment was getting a different error being thrown than in my local environment. I've changed it to a generic .toThrow() expectation for now, but would appreciated any advice if someone knows why there was a difference.

Local: 'undefined' is not a function (evaluating 'SampleNamespace.ComponentC(null )')
Travis: Object #<Object> has no method 'ComponentC'

Based on the error messages, it seems that it's a difference between running SampleNamespace.ComponentC(null) vs. new SampleNamespace.ComponentC(null), but I'm not sure why the compiled JSX would be different.

[syranide]

Discussed at length in #760

[percyhanna]

I hadn't noticed the extensiveness of that discussion before I began working on the PR. The syntax of defining the namespaces could be easily changed, if an alternate is desired.

[zpao]

Thanks for taking a stab at this. We're going to nail down our stance on namespacing in JSX and the strategy we want to follow ASAP.

[magalhas]

👍

[kendagriff]

+1 I also just got started on React.js, and almost immediately ran into wanting namespacing support in JSX.

[LBRapid]

👍 Namespacing support would be splendid.

[percyhanna]

Closing in favour of proposed fix in #760.