Emit addition recess error information when error occurs.

This commit lets us do fun things like this gist: https://gist.github.com/shellscape/d60b941e78736c3ccd82 when an error occurs. 

The ```fileName``` property was being lost when PluginError was instantiated. (PluginError's constructors are problematic and inconsistent, I've opened an issue with gulp-util about it). So I'm manually attaching it to the instance to ensure that it's not lost.
> If we overrode the line property for either case in favor of the other, we'd be losing important information

Well you already override the `fileName` property to point at the CSS/LESS file instead of the JS.

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I'm willing to add this if you open a good issue on gulp-util about my previous comment, on improving the gulp-util error constructor.