Be more intentional with URL parsing

[cansavvy]

This is attempting to address: jhudsl/ottrpal#142

Now we are parsing URLs based on how they are given in the content.

I think I've covered the major categories and any "http" strings that are detected that aren't in a particular type of format will still be attempted to be tested, but we'll parse them based on the major categories first before resorting to a catch all method attempt.

  all_tags <- c(html = html_tag, 
                knitr = include_url_tag, 
                ottrpal = include_slide_tag, 
                markdown = markdown_tag, 
                markdown_bracket = markdown_tag_bracket, 
                other_http = http_gen)

The only thing that is not addressed here is that if multiple URLS are in one sentence, only the first URL would be tested.