Soothe JSHint which cries about "Mixed spaces and tabs."

```
$ grunt jshint
Running "jshint:app" (jshint) task
>> 9 files lint free.

Running "jshint:tooling" (jshint) task
>> 29 files lint free.

Running "jshint:tests" (jshint) task
Linting tests/testem.js ...ERROR
[L9:C3] W099: Mixed spaces and tabs.
 *     <script src="/testem.js"></script>

Done, without errors.
```
Merge pull request #406 from pangratz/soothe_jshint

Soothe JSHint which cries about "Mixed spaces and tabs."