Gulp with minify css script

gulpfile.js

var gulp = require('gulp'),
    concat = require("gulp-concat"),
    cssmin = require("gulp-cssmin"),
    uglify = require("gulp-uglify");

gulp.task("min-css", function () {

    // Deploy bootstrap
    gulp.src("bower_components/bootstrap/dist/fonts/*")
        .pipe(gulp.dest("fonts"));

    gulp.src("bower_components/bootstrap/dist/js/*.min.js")
        .pipe(gulp.dest("Scripts"));

    // Compress site.css and bootstrap.css
    gulp.src(["bower_components/bootstrap/dist/css/bootstrap.min.css",
                "Content/site.css"])
        .pipe(concat("Content/site.min.css"))
        .pipe(cssmin())
        .pipe(gulp.dest("."));

});