#5850 - Add QR code to API credentials

This uses https://github.com/jeromeetienne/jquery-qrcode for generating
the QR code.

This is what it looks like:

![see screen shot](http://cld.wthms.co/11wpb+)

It’s small, **but**, it scans perfectly without any issues.

It contains both keys separated by a pipe character, like:

```
consumer_key|consumer_secret
```

Rather than making users scan 2 QR codes, etc.