title: gulp default, Task never defined: default, Please check the documentation for proper gulpfile formatting
body: <p>I checked out my project on a new machine and get an unsatisfying console output.  </p>
  
  <p><strong>Console Output</strong><br>
  gulp default<br>
  Using gulpfile ...\gulpfile.js<br>
  Task never defined: default<br>
  Please check the documentation for proper gulpfile formatting  </p>
  
  <p><strong>gulp -v</strong><br>
  CLI version 1.2.2<br>
  Local version 4.0.0-alpha.2  </p>
  
  <p><strong>Settings</strong><br>
  Node interpreter: nodejs-6.9.2\node.exe<br>
  Gulp package: node_modules\gulp-4.0.build  </p>
  
  <p><strong>Gulp File Content</strong>  </p>
  
  <pre><code>'use strict';
  var gulp = require('gulp');
  var del = require('del');
  var path = require('path');
  var sass = require('gulp-sass');
  var ts = require('gulp-typescript');
  var gulpPromise = require("gulp-promise");
  var gulpPromiseAll = require('gulp-all');
  var merge = require('merge-stream');
  var through = require('through2');
  var runSequence = require('run-sequence');
  var async = require("async");
  var Rx = require('rx');
  var chok = require('chokidar');
  var deleteEmpty = require('delete-empty');
  var browserSync = require('browser-sync').create();
  var webserver = require('gulp-webserver');
  var historyApiFallback = require('connect-history-api-fallback');
  
  /* A few functions like this */
  var yadda1 = function() {
      return yadda9("yadda", yaddayadda);
  };
  
  /* A few tasks like this */
  gulp.task('build', function(){
      return gulpPromiseAll(
          yadda1(),
          yadda2(),
          yadda3()
      ).then(
          function() {
              console.log("yadda");
          }, function(err) {
              console.error("yadda:", err);
          }
      );
  });
  
  gulp.task('default', gulp.series('build', 'serve', function(done) {
      console.log("Default task that cleans, builds and runs the application [END]");
      done();
  }));
  </code></pre>
  
  <p>What am I doing wrong?</p>