title: How to specify which child taks to run on watch grunt config
body: <p>I have the following watch configuration that reloads the page and run others tasks.</p>
  
  <pre><code>watch: {
              js: {
                  files: ['gruntfile.js', 'server.js', 'app/**/*.js', 'public/js/**', 'test/**/*.js'],
                  tasks: ['jshint'],
                  options: {
                      livereload: true,
                  },
              },
              html: {
                  files: ['public/views/**', 'app/views/**'],
                  options: {
                      livereload: true,
                  },
              },
              css: {
                  files: ['public/css/**'],
                  options: {
                      livereload: true
                  }
              },
              test: {
                  files: ['app/**/*.js', 'test/mocha/**/*.js'],
                  tasks: ['mochaTest', 'karma:unit']
              }
          },
  </code></pre>
  
  <p>I don't want to run the "test" option inside watch task, I just want to run it when I specify that, like in my test task:</p>
  
  <pre><code>grunt.registerTask('test-w', ['mochaTest', 'karma:unit', 'watch:test']);
  </code></pre>
  
  <p>I've tried to do this inside concurrent task:</p>
  
  <pre><code>tasks: ['nodemon', 'watch:js:html:css']
  </code></pre>
  
  <p>Didn't work unfortunetly :(</p>