gulpfile configuration for nunjucks and scss. also you can use npm run start for dev-enviorment or npm run build:prod which will minify your data for production

gulpfile.js

require('es6-promise').polyfill();

'use strict';

var gulp = require('gulp');
var sass = require('gulp-sass');
var sourcemaps = require('gulp-sourcemaps');
var autoprefixer = require('gulp-autoprefixer');
var uglify = require('gulp-uglify');
var jshint = require('gulp-jshint');
var jslint = require('gulp-jslint');
var jsinclude = require('gulp-include');
var concat = require('gulp-concat');
var del = require('del');
var order = require('gulp-order');
var nunjucksRender = require('gulp-nunjucks-render');
var htmlmin = require('gulp-htmlmin');
var htmlhint = require("gulp-htmlhint");

var bases = {
    source: 'src/',
    dist: 'dist/',
    node_modules: 'node_modules/',
    sourcemap: 'maps/'
};

var paths = {
    scripts: [
        bases.source + 'js/index.js',
        bases.source + 'js/all.js'
    ],
    styles: [
        bases.source + 'scss/style.scss'
    ],
    html: [ '**/*.nunjucks' ],
    fonts: [
        bases.source + 'fonts/**',
    ],
    images: [
        bases.source + 'images/**',
    ]
};

var production = false;

gulp.task('clean', function() {
    return del([
        bases.dist,
        './npm-debug.log'
    ]);
});

gulp.task('sass', function () {
    var sassOptions;
    var t = gulp.src(paths.styles)
    .pipe(sourcemaps.init())
    .pipe(sass.sync().on('error', sass.logError));

    if (production) {
        sassOptions = {outputStyle: 'comporessed'};
    }

    t=t.pipe(sass(sassOptions).on('error', sass.logError));

    if (production) {
        t=t.pipe(autoprefixer({
            browsers: ['IE>=11', 'iOS >=8', 'android >=4.4', 'last 3 version']
        }));
    }

    return t.pipe(sourcemaps.write(bases.sourcemap))
    .pipe(gulp.dest(bases.dist));
});

gulp.task('javascript', function() {
    var t = gulp.src(paths.scripts)
        .pipe(jsinclude({
            extensions: "js",
            hardFail: true,
            includePaths: [
                __dirname + "/node_modules",
                __dirname + "/src/js"
            ]
        }))
        .on('error', console.log)
        .pipe(order(paths.scripts, { base: './' }))
        .pipe(sourcemaps.init());

    if(production) {
        t=t.pipe(uglify({
            output: { beautify: false }
        }));
    }

    t=t.pipe(concat('all.js'))
        .pipe(sourcemaps.write('.', {
            includeContent:false
        }))
        .pipe(gulp.dest(bases.dist + 'js/'));

    return t;
});

gulp.task('javascript:lint', function() {
    return gulp.src(paths.scripts)
        .pipe(jslint())
        .pipe(jslint.reporter('default'));
});

gulp.task('javascript:hint', function() {
    return gulp.src(paths.scripts)
        .pipe(jshint())
        .pipe(jshint.reporter('default'));
});

gulp.task('nunjucks', function () {
    nunjucksRender.nunjucks.configure([bases.source]);
    var t =  gulp.src(bases.source + '*.nunjucks')
        .pipe(nunjucksRender())
        .pipe(htmlhint())
        .pipe(htmlhint.reporter());

    if(production) {
        t=t.pipe(htmlmin({ collapseWhitespace: true }));
    }

    t=t.pipe(gulp.dest(bases.dist));

    return t;
});

gulp.task('fonts', function() {
    return gulp.src(paths.fonts)
        .pipe(gulp.dest(bases.dist + 'fonts/'));
});

gulp.task('images', function() {
    return gulp.src(paths.images)
        .pipe(gulp.dest(bases.dist + 'img/'));
});

var tinylr;

gulp.task('livereload', function() {
    tinylr = require('tiny-lr')();
    tinylr.listen(35729);
});

function notifyLiveReload(event) {
    var fileName = require('path').relative(__dirname, event.path);

    tinylr.changed({
        body: {
            files: [fileName]
        }
    });
}

gulp.task('watch', function() {
    gulp.watch(bases.source + 'css/*.css', ['sass']);
    gulp.watch(bases.source + 'scss/*.scss', ['sass']);
    gulp.watch(bases.source + 'js/*.js', ['javascript']);
    gulp.watch(bases.source + '**/*.html', ['nunjucks']);
    gulp.watch(bases.source + '**/*.nunjucks', ['nunjucks']);
    gulp.watch(bases.dist + '**/*', notifyLiveReload);
});

gulp.task('express', function () {
    var express = require('express');
    var app = express();

    app.get('/hello', function(req, res) {
        res.send({ message: 'world' });
    });
    app.get('/hello.json', function(req, res) {
        res.json({ message: 'world' });
    });

    app.use(require('connect-livereload')({port: 35729}));
    app.use(express.static(bases.dist));

    app.use(function(req, res, next) {
        res.status(404).send('Sorry cant find that!');
    });

    app.use(function(err, req, res, next) {
        console.error(err.stack);
        res.status(500).send('Something broke!');
    });

    app.listen(4000, '0.0.0.0');
});

gulp.task('set-env-production', function() {
    production = true;
});

gulp.task('default', ['sass', 'javascript', 'nunjucks', 'fonts', 'images', 'livereload', 'express', 'watch']);

gulp.task('build:dist', ['sass', 'javascript', 'nunjucks', 'fonts', 'images']);

gulp.task('build:prod', ['set-env-production', 'build:dist']);