title: CSS Sourcemaps not generating properly with gulp, SASS, & autoprefixer
body: <p>I have the following gulp task:</p>
  
  <pre><code>var gulp = require('gulp'),
      sass = require('gulp-ruby-sass'),
      autoprefixer = require('gulp-autoprefixer');
  
  gulp.src('html/css/sass/*.scss')
      .pipe(sass({
          style: 'compressed',
          loadPath: 'plugin/css/sass',
          sourcemap: true,
          sourcemapPath: '/css/sass',
          container : 'local_sass'
      }))
      .pipe(autoprefixer())
      .pipe(gulp.dest('html/css'));
  </code></pre>
  
  <p>The problem I'm having is the SASS compiler is properly generating the sourcemaps and adding the sourcemap comment, but then autoprefixer removes the comment (and I don't think it's updating the sourcemaps either). </p>
  
  <p>I've tried removing autoprefixer and it works perfectly, but when I put it back in, they comment is removed. I also tried adding <code>{ map: true }</code>, but then each sourcemap just has the name <code>to.css.map</code>. I also tried adding <code>from</code> and <code>to</code> but I don't know how to do tell it current filename so it always writes to the same filename.</p>
  
  <p>How would I go about getting autoprefixer to co-operate and <strong>update the sourcemaps</strong>? Is there another plugin I need to use?</p>
  
  <p>Packages:</p>
  
  <pre><code>"gulp": "~3.8.6",
  "gulp-autoprefixer": "~0.0.8",
  "gulp-ruby-sass": "~0.7.0",
  </code></pre>