Further fix to #553: Allow caching but using our digesting to bust it.
Further fix to #553: Allow caching but using our digesting to bust it.

jekyll-assets/jekyll-assets,jekyll/jekyll-assets,mattbeedle/jekyll-assets,mattbeedle/jekyll-assets,jeremy/jekyll-assets,jekyll-assets/jekyll-assets,jekyll-assets/jekyll-assets,jekyll/jekyll-assets,jeremy/jekyll-assets,mattbeedle/jekyll-assets,jekyll/jekyll-assets,mattbeedle/jekyll-assets,jeremy/jekyll-assets,jekyll/jekyll-assets,jeremy/jekyll-assets