gulp.task('amp-sass-clean-up', ['amp-sass' /*Add gulp-sass task that compiles CSS*/], function() {
    return gulp
        .src(['/public/amp.min.css' /*This is the full path and file name to where your final css is*/], {cwd: '/public' /*This is the full path to where final css file is*/)
        .pipe(replace('@charset "UTF-8";', ''))
        .pipe(gulp.dest('/public' /*This is the full path to where final css file is*/);
});