update dependencies and gulpfile.js to gulp 4

bootstrap 4.2.1, font awesome 5.6.3, gulp 4, and gulpfile rewritten for gulp 4

.travis.yml

@@ -1,5 +1,6 @@
-sudo:          false
 language:      node_js
+git:
+  depth:       3
 node_js:
   - "node"
 install:       npm install
@@ -9,3 +10,5 @@ script:
 cache:
   directories:
     - node_modules
+notifications:
+  email:       false

gulpfile.js

@@ -1,15 +1,17 @@
-var gulp = require('gulp');
-var sass = require('gulp-sass');
-var header = require('gulp-header');
-var cleanCSS = require('gulp-clean-css');
-var rename = require("gulp-rename");
-var uglify = require('gulp-uglify');
-var autoprefixer = require('gulp-autoprefixer');
-var pkg = require('./package.json');
-var browserSync = require('browser-sync').create();
+// Load plugins
+const autoprefixer = require("gulp-autoprefixer");
+const browsersync = require("browser-sync").create();
+const cleanCSS = require("gulp-clean-css");
+const gulp = require("gulp");
+const header = require("gulp-header");
+const plumber = require("gulp-plumber");
+const rename = require("gulp-rename");
+const sass = require("gulp-sass");
+const uglify = require("gulp-uglify");
+const pkg = require('./package.json');
 
 // Set the banner content
-var banner = ['/*!\n',
+const banner = ['/*!\n',
   ' * Start Bootstrap - <%= pkg.title %> v<%= pkg.version %> (<%= pkg.homepage %>)\n',
   ' * Copyright 2013-' + (new Date()).getFullYear(), ' <%= pkg.author %>\n',
   ' * Licensed under <%= pkg.license %> (https://github.com/BlackrockDigital/<%= pkg.name %>/blob/master/LICENSE)\n',
@@ -18,7 +20,7 @@ var banner = ['/*!\n',
 ].join('');
 
 // Copy third party libraries from /node_modules into /vendor
-gulp.task('vendor', function() {
+gulp.task('vendor', function(cb) {
 
   // Bootstrap
   gulp.src([
@@ -41,76 +43,83 @@ gulp.task('vendor', function() {
     ])
     .pipe(gulp.dest('./vendor/jquery'))
 
+  cb();
+
 });
 
-// Compile SCSS
-gulp.task('css:compile', function() {
-  return gulp.src('./scss/**/*.scss')
-    .pipe(sass.sync({
-      outputStyle: 'expanded'
-    }).on('error', sass.logError))
+// CSS task
+function css() {
+  return gulp
+    .src("./scss/*.scss")
+    .pipe(plumber())
+    .pipe(sass({
+      outputStyle: "expanded"
+    }))
+    .on("error", sass.logError)
     .pipe(autoprefixer({
       browsers: ['last 2 versions'],
       cascade: false
     }))
     .pipe(header(banner, {
       pkg: pkg
     }))
-    .pipe(gulp.dest('./css'))
-});
-
-// Minify CSS
-gulp.task('css:minify', ['css:compile'], function() {
-  return gulp.src([
-      './css/*.css',
-      '!./css/*.min.css'
-    ])
-    .pipe(cleanCSS())
+    .pipe(gulp.dest("./css"))
     .pipe(rename({
-      suffix: '.min'
+      suffix: ".min"
     }))
-    .pipe(gulp.dest('./css'))
-    .pipe(browserSync.stream());
-});
-
-// CSS
-gulp.task('css', ['css:compile', 'css:minify']);
+    .pipe(cleanCSS())
+    .pipe(gulp.dest("./css"))
+    .pipe(browsersync.stream());
+}
 
-// Minify JavaScript
-gulp.task('js:minify', function() {
-  return gulp.src([
+// JS task
+function js() {
+  return gulp
+    .src([
       './js/*.js',
-      '!./js/*.min.js'
+      '!./js/*.min.js',
+      '!./js/contact_me.js',
+      '!./js/jqBootstrapValidation.js'
     ])
     .pipe(uglify())
-    .pipe(rename({
-      suffix: '.min'
-    }))
     .pipe(header(banner, {
       pkg: pkg
     }))
+    .pipe(rename({
+      suffix: '.min'
+    }))
     .pipe(gulp.dest('./js'))
-    .pipe(browserSync.stream());
-});
-
-// JS
-gulp.task('js', ['js:minify']);
+    .pipe(browsersync.stream());
+}
 
-// Default task
-gulp.task('default', ['css', 'js', 'vendor']);
+// Tasks
+gulp.task("css", css);
+gulp.task("js", js);
 
-// Configure the browserSync task
-gulp.task('browserSync', function() {
-  browserSync.init({
+// BrowserSync
+function browserSync(done) {
+  browsersync.init({
     server: {
       baseDir: "./"
     }
   });
-});
+  done();
+}
 
-// Dev task
-gulp.task('dev', ['css', 'js', 'browserSync'], function() {
-  gulp.watch('./scss/*.scss', ['css']);
-  gulp.watch('./js/*.js', ['js']);
-  gulp.watch('./*.html', browserSync.reload);
-});
+// BrowserSync Reload
+function browserSyncReload(done) {
+  browsersync.reload();
+  done();
+}
+
+// Watch files
+function watchFiles() {
+  gulp.watch("./scss/**/*", css);
+  gulp.watch(["./js/**/*.js", "!./js/*.min.js"], js);
+  gulp.watch("./**/*.html", browserSyncReload);
+}
+
+gulp.task("default", gulp.parallel('vendor', css, js));
+
+// dev task
+gulp.task("dev", gulp.parallel(watchFiles, browserSync));