Migrate the NFL feeds from XML to JSON

This pull request supersedes #36. I was not happy with the fact that MLB was modified with all of the NFL JSON changes. I am going split them out. The MLB changes will be made as their own pull request (tbd). 
Space missing to the left of {.<br>Space between { and | missing.<br>Space missing inside }.<br>Prefer double-quoted strings unless you need single quotes to avoid extra backslashes for escaping.