message: follow_me: draw simple square, fix crazy counting
  This changes the follow me path to just a simple square.
  Also, this fixes a previous bug where it rushed through the locations
  too quickly because each if would increment count_.
diff: @@ -37,39 +37,30 @@ void FakeLocationProvider::stop()
  }
  }
  -// Rudimentary location provider whose successive lat, lon combination
  -// makes Drone revolve in a semi-circular path.
  +// Rudimentary location provider to draw a square.
  void FakeLocationProvider::compute_locations()
  {
  while (!should_exit_) {
  - if (count_++ < 10) {
  + if (count_ < 10) {
  location_callback_(latitude_deg_, longitude_deg_);
  latitude_deg_ -= LATITUDE_DEG_PER_METER * 4;
  - }
  - if (count_++ < 20) {
  + } else if (count_ < 20) {
  location_callback_(latitude_deg_, longitude_deg_);
  longitude_deg_ += LONGITUDE_DEG_PER_METER * 4;
  - }
  - if (count_++ < 30) {
  + } else if (count_ < 30) {
  location_callback_(latitude_deg_, longitude_deg_);
  latitude_deg_ += LATITUDE_DEG_PER_METER * 4;
  - }
  - if (count_++ < 40) {
  + } else if (count_ < 40) {
  location_callback_(latitude_deg_, longitude_deg_);
  longitude_deg_ -= LONGITUDE_DEG_PER_METER * 4;
  - }
  - if (count_++ < 50) {
  - location_callback_(latitude_deg_, longitude_deg_);
  - latitude_deg_ -= LATITUDE_DEG_PER_METER * 3;
  - }
  - if (count_++ < MAX_LOCATIONS) {
  - location_callback_(latitude_deg_, longitude_deg_);
  - longitude_deg_ += LONGITUDE_DEG_PER_METER * 3;
  + } else {
  + // We're done.
  + should_exit_ = true;
  }
  sleep_for(seconds(1));
  + ++count_;
  }
  }
  -const size_t FakeLocationProvider::MAX_LOCATIONS = 60u;
  const double FakeLocationProvider::LATITUDE_DEG_PER_METER = 0.000009044;
  const double FakeLocationProvider::LONGITUDE_DEG_PER_METER = 0.000008985;
  