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 :)
Not sure if || is more appropriate here, when for example noEmitOnError is true and there are errors and record is not undefined (because getSourceMapRecord returned a sourcemap).. then it should actually try to compare them right?