TypeScript files hould be able to import other TypeScript files

[Kevin Phillips]

This situation fails currently because it will try to load greeter.js and then greeter/index.js:

// index.ts
import Greeter from "./greeter";
var greeter = new Greeter("Hello, world!");
document.body.innerHTML = greeter.greet();

// greeter.ts
export default class Greeter {
    constructor(public greeting: string) { }
    greet() {
        return "<h1>" + this.greeting + "</h1>";
    }
};