code: function getPreview (post, body, options) {
    var readMoreTag = options.readMoreTag || post.readMoreTag;
    var preview;
    if (post.preview) {
      preview = post.preview;
    } else if (post.previewLength) {
      preview = body.trim().substr(0, post.previewLength);
    } else if (~body.indexOf(readMoreTag)) {
      preview = body.split(readMoreTag)[0];
    } else {
      preview = body.trim().replace(/\n.*/g, '');
    }
  
    return preview;
  }
docs: Takes a `post` object, `body` text and an `options` object
  and generates preview text in order of priority of a `preview`
  property on the post, then `previewLength`, followed by
  finding a `readMoreTag` in the body.
  
  Otherwise, use the first paragraph in `body`.
  
  @params {Object} post
  @params {String} body
  @params {Object} options
  @return {String}