added json.html.markdown

Very short and slightly silly, but I think it works.
slightly expanded on json.html.markdown

Removed useless stuff, added new stuff.
added learnjson.json

Forgot this thing, oops.
removed learnjson.json. i am so confused.

I think it automatically generates it? I can't tell.
Merge pull request #553 from iirelu/json

[json/en] Added JSON.