Using error notification when code errors

Currently brackets only shows the warning style notify icon when there the `CodeInspector` finds problems with the code. This change means it will now show the error icon if any of the errors have the `error.type = Type.ERROR`

Not the worlds biggest fan of the icon but it was already present. If you'd like it changing for a different one let me know. 

![image](https://cloud.githubusercontent.com/assets/2362687/5047869/362a11b2-6c11-11e4-9590-57d6f8a99d1e.png)

This is particularly useful for my Omnisharp plugin :)

Thanks for adding unit tests!

For clarity, message should say "warnings" instead of "errors" since type is WARNING.