Status bar summary

![screen shot 2014-12-03 at 21 46 54](https://cloud.githubusercontent.com/assets/1850538/5288679/499f3e68-7b37-11e4-9555-53dee1cf3f9e.png)

So it display the number of errors/warning.

Let me know if you need further information about the commit.
what is `errorsNb`? I don't see it declared anywhere.