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/
Listen for 'input' events on the sliders.

This triggers events whenever the sliders move, updating the state
of the blink(1) in real-time.
Add link to documentation for blink(1) commands.

Explain where the magic numbers sent in the HID feature report come
from.
blink(1) command buffer is only 7 bytes.

The first byte (as shown in the documentation) is the feature report ID
and is inserted automatically by the chrome.hid API as necessary.
blink1: Switch back to 8-byte feature reports.

Correction to 3be484ba614fb16a6014cca5ef6a943d3c821ce4, even though only
7 bytes of the command buffer are used the feature report is declared as
8 bytes in the HID report descriptor. Windows requires a full buffer to
be sent or else the transfer fails with a CRC error so provide that here.
blink1: Check devices.length >= 1.

If device enumeration succeeds there may be no devices in the array passed
to the callback. There should really be a selector of some sort to choose
which device to control.
Merge pull request #277 from reillyeon/blink1

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