Output '{' in console will make test failed

if we run `console.warn('..... function _Class() {....}')` during test, we will got

```
events.js:141
throw er; // Unhandled 'error' event
^
SyntaxError: Unexpected token o
at Object.parse (native)
at /Users/jareguo/firebox/fireball/node_modules/gulp-qunit/index.js:51:40
at Array.forEach (native)
```

It seems like we should add use try catch here https://github.com/jonkemp/gulp-qunit/blob/master/index.js#L71