function sassFunc() {
return gulp.src('app/sass/*.sass')
.pipe(sass())
.pipe(autoprefixer(['last 7 versions', '> 1%', 'ie 8', 'ie 7'], { cascade: true}))
.pipe(gulp.dest('app/css'))
.pipe(browserSync.reload({stream: true}))
}
gulp.task('sass', sassFunc);