title: gulp.js strips relative paths of output files
body: <p>I have a gulp.js configuration set up to automatically compile my SASS and CoffeeScript on save. It works, except that the relative paths are totally lost, and all the files are output into a single flat directory. I would like to retain the sub-directory structure of my <code>app/assets/sass</code> and <code>app/assets/coffee</code> directories when the final CSS and JS files are compiled. Here is my gulpfile:</p>
  
  <pre><code>var gulp = require('gulp');
  var plumber = require('gulp-plumber');
  var gutil = require('gulp-util');
  var minifycss = require('gulp-minify-css');
  var autoprefixer = require('gulp-autoprefixer');
  var sass = require('gulp-ruby-sass');
  var coffee = require('gulp-coffee');
  
  var sassDir = 'app/assets/sass';
  var coffeeDir = 'app/assets/coffee';
  
  gulp.task('sass', function() {
      return gulp.src(sassDir + '/**/*.scss')
          .pipe(plumber())
          .pipe(sass({ style: 'compress' }).on('error', gutil.log))
          .pipe(autoprefixer('last 10 versions'))
          .pipe(minifycss())
          .pipe(gulp.dest('public/css'));
  });
  
  gulp.task('coffee', function() {
      return gulp.src(coffeeDir + '/**/*.coffee')
          .pipe(plumber())
          .pipe(coffee({ bare: true }).on('error', gutil.log))
          .pipe(gulp.dest('public/js/coffee)'));
  });
  
  gulp.task('watch', function() {
      gulp.watch(sassDir + '/**/*.scss', ['sass']);
      gulp.watch(coffeeDir + '/**/*.coffee', ['coffee']);
  });
  
  
  gulp.task('default', ['sass', 'coffee', 'watch']);
  </code></pre>