Better documentation for keeping both original and RTL styles

[Strajk]

Hi, first of all, thanks for great job...

I struggled a little bit with configuration for keeping original file generating rtl version next to it. Maybe would be helpful for others to include it in README.

var rename = require('gulp-rename');
var rtlcss = require('gulp-rtlcss');

gulp.task("styles", function (event) {
    return gulp.src("/styles/**.css")
        // process: e.g. pipe(autoprefixer({}))
        .pipe(gulp.dest(".tmp/styles/"))
        .pipe(rename(function (path) {
            path.basename += ".rtl";
        }))
        .pipe(rtlcss())
        .pipe(gulp.dest(".tmp/styles/"));
});

[jjlharrison]

Thanks for your suggestion. I've added a real-world example to the README.

[Strajk]

@jjlharrison awesome, thanks! :)