implemented treat warning as errors commandline option.

Same name as csc.exe uses: [msdn](http://msdn.microsoft.com/en-us/library/406xhdz3.aspx)
Issue #828

Feedback appreciated but feel free to close when you don't want this functionality at this point :)
Is there a situation in which `record` can be `undefined` but the condition `options.noEmitOnError && result.errors.length !== 0` evaluates to false? Perhaps a `||` is more appropriate?