fix BLEFirmataSketch for BlendMicro

hi!
I have developed [BLE Firmata library for node.js](https://github.com/shokai/node-ble-firmata).

but `BLEFirmataSketch.ino` in example sketch does not work on blendmicro, so I fixed it.

I have tested with blendmicro, checked functions are

- digitalRead
- digitalWrite
- analogRead
- analogWrite
- servoWrite
- REPORT_VERSION
- sysex command

I dont have BLE Shield so I checked only blendmicro, sorry.