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.
I'm not sure about this one: Should `chrome.hid.receiveFeatureReport` always be called AFTER `chrome.hid.sendFeatureReport` was called successfully? Is there any chance we could miss the receive event?