var gulp        = require('gulp'), 
    sass        = require('gulp-sass'), 
autoprefixer = require('gulp-autoprefixer'),
    browserSync = require('browser-sync'); 


gulp.task('sass', function(){ 
    return gulp.src(['app/sass/**/*.sass', 'app/sass/**/*.scss']) 
        .pipe(sass({outputStyle: 'expanded'}).on('error', sass.logError))
        .pipe(autoprefixer(['last 15 versions', '> 1%', 'ie 8', 'ie 7'], { cascade: true }))
        .pipe(gulp.dest('app/css')) 
        .pipe(browserSync.reload({stream: true})) 
});

.pipe(sass({outputStyle: 'expanded'}).on('error', sass.logError))
.pipe(autoprefixer(['last 15 versions', '> 1%', 'ie 8', 'ie 7'], { cascade: false}))

<ol style="display: table; margin:0 auto;">
		<li>Математика</li>
		<li>Физика</li>
		<li>Химия</li>
		<li>История</li>
		<li>Информатика</li>
	</ol>