Upload carbs-on-board to Nightscout

[mddub]

For mddub/urchin-cgm#50.

I would appreciate it if someone else (@ps2?) could test this before I merge. You should see something like this in /api/v1/devicestatus.json?find[loop][$exists]=1:

{
  "loop": {
    "cob": {
      "timestamp": "2016-10-20T23:40:00Z",
      "cob": 18.2929316872428
    }, ...
  }, ...
}

[ps2]

I see cob uploading to NS, and I see it showing in urchin! Very nice! It's not showing in the COB plugin in NS, but I believe that is just that NS needs to be updated to look there for Loop cob.

[ps2]

Just waiting to see it update. I reviewed the code and couldn't see anything to improve upon. Will approve once I see the update.

[ps2]

Thanks @mddub! Doing my work for me! :) I was planning on tackling this, but just didn't have the time. Great work.

[ps2]

I do see some occasional issue in NS about 'cob' being undefined, but that's probably more NS issues to work through.

[mddub]

Awesome! Thanks for reviewing and helping test!