Separate out blink(1) commands into blink1.js.

Create a separate Javascript class that represents a particular blink(1)
device and encapsulates the usage of the chrome.hid API.
It would be nice to have `vendorId` and `productId` defined in `Blink1` such as
    
    Blink1.VENDOR_ID = 10168; // 0x27B8
    Blink1.PRODUCT_ID = 493; // 0x01ED