Add Options.diff and refactor test to use it

Set Options through setOptions to check for unknown options.
Correct sourceMap -> sourceMaps
Fixes #1254
or

```js
var p;
if (traceurOptions.script)
  p = loader.script(contents, {});
else
  p = loader.module(contents, {});
p.then(onSuccess, onFailure);
```
or
```js
var p = traceurOptions.script ? loader.script(contents, {}) : loader.module(contents, {});
p.then(onSuccess, onFailure);
```