Add tags to JSON metadata #151
This adds the rest of the JSON fields to pass all errors and blog postings. - Adds page.image.url for the image url. (Will default to image if not present). - Add page.image.height and page.image.width for an image object (Will default back to image url if not present). - Add dateModified (will capture from yaml if present, if not it will use datePublished) - (I feel there should be a manual option for this as I sometimes save parts of my blog that shouldn't update the modified field, but still change the file timestamp). This should create JSON that will pass all warnings/strong recommendations/errors from [Google's Structured Data Testing Tool](https://search.google.com/structured-data/testing-tool).
Travis didn't like my date/dateModified tests because of time-zone issues. I had to pull those specific ones. Fixed up the rubocop styling.
Looks like everything is good for an inspection.
@benbalter @jhabdas Removed image changes from this PR. #174 is handling image changes. Should be more straight forward if it's ok having these changes in a single PR. If not, I can continue pulling these out, but they seem to go together.
Additions in this PR exist to appease Google Structured Data Testing Tool.