title: Gulp task not exit properly
body: <p>I have the following install task :</p>
  
  <pre><code>gulp.task('install', ['createInfraIniFile']);
  
  gulp.task('createAppIni', function () {
  
     return gulp.src('')
      .pipe(prompt.prompt([{
          type: 'input',
          name: 'version',
          message: 'Please enter the version ?'
      }], function(res){
          var config = ini.parse(fs.readFileSync('./ini/test_sample.ini', 'utf-8'));
  
          // Write params into app.ini file
          config.DATA.version = res.version;
  
          fs.writeFileSync('./ini/test.ini', ini.stringify(config));
      }));
  
  });
  
  gulp.task('createInfraIniFile', ['createAppIni'], function () {
  
     return gulp.src('')
      .pipe(prompt.prompt([{
          type: 'input',
          name: 'version',
          message: 'Please enter url'
      }], function(res){
          var config = ini.parse(fs.readFileSync('./ini/conf_sample.ini', 'utf-8'));
  
          // Write params into app.ini file
          config.DATA.url = res.url;
  
          fs.writeFileSync('./ini/conf.ini', ini.stringify(config));
      }));
  
  });
  </code></pre>
  
  <p>This task executes the createAppIni task first and then, the createInfraIniFile. But at the end, gulp doesn't stop execution :</p>
  
  <p><a href="https://i.stack.imgur.com/LP5J7.jpg" rel="nofollow"><img src="https://i.stack.imgur.com/LP5J7.jpg" alt="enter image description here"></a></p>
  
  <p>When i execute a single task, it works fine. Where is my mistake ?</p>