sourceMappingURL relative root

in the following example 

gulp.task('js', function() {
    return gulp.src('source/clientside/**/*.js')
        .pipe(map('all.js', {
            prefix: 2,
            sourceRelavtiveBase: '/scripts/'
        }))
        .pipe(gulp.dest('dist/scripts'))
}); 

The source map url needs to be relative to site base. (E.g. //# sourceMappingURL=/scripts/all.js.map)
This option allows for the user to change the relative path.