added optional settings to manipulate the destination path

[nd0]

Hi Mike,

First of all, thanks for this great package!
I added two optional settings to control the destination path.

For expample a given file /my/path/main.js should uploaded to /etc/designs/myproject/clientlib-site/main.js.

var src = '/my/path';
gulp.task('watch', function() {
    gulp.watch(src + '/**/*', function(e) {
        return gulp.src()
            .pipe(slang({
                base: src,
                dest: '/etc/designs/myproject/clientlib-site'
            }));
    });
});

Best regards
Nils