Getting rid of unwanted output in the specs (from JS output)

Gets rid of output  like this:

```
2014-03-21 15:12:22.114 phantomjs[88442:507] CoreText performance note: Client called CTFontCreateWithName() using name "Helvetica Neue" and got font with PostScript name "HelveticaNeue". For best performance, only use PostScript names when calling this API.
```

https://github.com/ariya/phantomjs/issues/11418
https://gist.github.com/ericboehs/7125105