Add support for getting elections from JSON

[GPHemsley]

For example: http://results.enr.clarityelections.com/CO/elections.json

[dwillis]

Yeah, this would be very useful in generating URLs.

[carbonphyber]

While desirable, I ran through all 50 states and very few (maybe 4) actually have this URL which responds with a JSON which is non-empty and those which do are not comprehensive.

AFAICT this URL is probably manually created and not often updated.