title: Gulp js running twice for the watch statement
body: <p>I see the console log statement that js task run twice once I change any of the javascript files. I wonder why it run two times for each change?</p>
  
  <pre><code>var gulp = require('gulp');
  var concat = require("gulp-concat");
  var uglify = require("gulp-uglify");
  
  gulp.task('default', function() {
      gulp.watch("public/js/**/*.*", ["js"]);
  });
  
  gulp.task("js", function(){
      var js = [
          "public/js/**/*.js",
          "!public/js/api/**/*.js"
      ];
  
      gulp.src(js)
      .pipe(concat("app.min.js"))
      .pipe(uglify())
      .pipe(gulp.dest("public/js"));
  });
  </code></pre>
  
  <p>Console</p>
  
  <pre><code>[13:02:27] Starting 'js'...
  [13:02:27] Finished 'js' after 1.6 ms
  [13:02:27] Starting 'js'...
  [13:02:27] Finished 'js' after 5.1 ms
  </code></pre>