message: README.md: update MMA7660 snippet to reflect current reality
diff: @@ -37,21 +37,13 @@ A sensor/actuator is expected to work as such (here is the MMA7660 accelerometer
  accel->setModeStandby();
  // enable 64 samples per second
  - accel->setSampleRate(upm::MMA7660::AUTOSLEEP_64);
  + accel->setSampleRate(MMA7660_AUTOSLEEP_64);
  // place device into active mode
  accel->setModeActive();
  while (shouldRun)
  {
  - int x, y, z;
  -
  - accel->getRawValues(&x, &y, &z);
  - cout << "Raw values: x = " << x
  - << " y = " << y
  - << " z = " << z
  - << endl;
  -
  float ax, ay, az;
  accel->getAcceleration(&ax, &ay, &az);
  