Merge branch 'fix_command_typing_with_status' of https://github.com/luckydonald/tg into luckydonald-fix_command_typing_with_status

[commands] Fix for ```send_video``` failing without a caption string given.

[json] Add user online status event

That's what you get when using regexes...

(see https://github.com/vysheng/tg/issues/538)

E.g. ```{"event": "online-status", "online": true, "when": "2015-05-20 00:16:40", "state": 1, "user": {"username": ... }}```

E.g. ```{"event": "online-status", "online": true, "when": "2015-05-20 00:16:40", "state": 1}```

E.g. ``` {  ... ,   "type":"typing", "status":"recording audio",  ... }```

Added output when message are marked read (if ```--json```), which fixes Issue [#516] (https://github.com/vysheng/tg/issues/516#issuecomment-101710890)
Also added event field to json which will be send to terminal/main_session:
"event" = "message", "read" (message got read), "service", (events only in secret chats?)  "updates" (peer name change etc), "download" (file downloaded)