blink1: Sample HID app to control a blink(1) mk2 device.

This app demos the new chrome.hid API by controlling a blink(1) mk2 RGB
LED light. More interesting features (don't love RGB sliders?) coming soon!

http://blink1mk2.thingm.com/
Just gave it a try now and if there is no plugged device I still get this error in my background page with `39.0.2136.0 (Developer Build b1748b82e821)`:

```javascript
Error in response to hid.getDevices: TypeError: Cannot read property 'deviceId' of undefined
    at Object.onDevicesEnumerated [as callback] (chrome-extension://jgabncbhbaehellmpdpbjjalgmnjjnkg/color-picker.js:46:34)
    at enumerateDevices (chrome-extension://jgabncbhbaehellmpdpbjjalgmnjjnkg/color-picker.js:34:16)
    at initializeWindow (chrome-extension://jgabncbhbaehellmpdpbjjalgmnjjnkg/color-picker.js:24:5)