adds real vinyl stream and improves paths

[ghost]

nunjucks task now looks something like this:

gulp.task('nunjucksGenerated', ['json'], function() {
  return generateVinyl(options.path, options.dataPath)
  .pipe(plumber())
//...

and the following configurable options are available for the URLs:

var options = {
  hashLength: 7, // length to truncate hash for page urls
  slugLength: 128, // length to truncate title slug for page urls
  useId: // whitelist for data files to use an id hash in the url, all others will just be title slug
  [
  'papers.json'
  ]
}

this can be merged post-release

[claudioccm]

nor merging before launch. Revisit later