title: How to get sourcemaps for gulp+babel+browserify+uglify
body: <p>I am using gulp to bundle browserify+babelify with uglifyjs. O
  However, the sourcemaps generated from my project only give me the bundled version, not the bundled version. </p>
  
  <p>Here is my setup:</p>
  
  <pre><code>var gulp       = require('gulp'),
      source     = require('vinyl-source-stream'),
      browserify = require('browserify'),
      gutil      = require('gulp-util'),
      buffer     = require('vinyl-buffer'),
      sourcemaps = require('gulp-sourcemaps'),
      uglify     = require('gulp-uglify'),
      file       = 'index.js';
  
  gulp.task('build', function(){
      return browserify({
          entries: [file],
          transform: ["babelify"]
        })
      .bundle()
      .pipe(source(file))
      .pipe(buffer())
      .pipe(sourcemaps.init({loadMaps: true}))
      .pipe(uglify())
      .pipe(sourcemaps.write('./'))
      .pipe(gulp.dest('./public/js'))
      .pipe(gutil.noop())
  })
  </code></pre>
  
  <p>Is there a way for me to create a build that bundles babel=>browserify=>uglify and still return me maps to my pre-babel files?</p>
  
  <p>I also don't mind not using gulp (I actually prefer grunt but this setup used to work for me in the past).</p>