Remove global `React` lookup during runtime

This removes the global `React` lookup that was happening within the React Intl Components' `render()` methods. A new local `react` module has been created to provide the reference to the `React` object.

**Note:** This is a temp solution, the real fix we want is to update the ES6 Module Transpiler to poperly deal with external, non ES6 modules.

Closes #47