Hack around TypeScript's broken handling of export class with ES6 modules and ES5 script target.

It works because TypeScript transforms

export class A {}

into something like CommonJS, when we wanted ES6 modules.

var A = (function () {
    function A() {
    }
    return A;
}());
exports.A = A;

But

class A {}
export { A };

is transformed into this beauty.

var A = (function () {
    function A() {
    }
    return A;
}());
export { A };

The solution is to replace the previous export syntax with the latter. The changes in this PR can be reverted once TypeScript supports this natively.

We also ensure that errors are reported for the current file.

Fixes #9
Includes #10