problems formatting fat arrow functions

clang-format@1.0.12 insists that this is the right way to format the following code:

```
module.exports = function makeNodeTree(destinationPath) {

  var traceurCompatibleTsModulesTree = replace(modulesTree, {
    replaceWithPath: (path, content) => {
      return content;
}
});
}
;
```

removing the fat arrow section or the return statement from the fat arrow block makes things work fine again.
