message: Fixed some pre-existing linter complaints while I was here.
diff: -#ifndef VOXBLOX_CORE_IO_LAYER_IO_INL_H_
  -#define VOXBLOX_CORE_IO_LAYER_IO_INL_H_
  +#ifndef VOXBLOX_IO_LAYER_IO_INL_H_
  +#define VOXBLOX_IO_LAYER_IO_INL_H_
  #include <fstream>
  +#include <string>
  #include "voxblox/Block.pb.h"
  #include "voxblox/Layer.pb.h"
  @@ -244,4 +245,4 @@ bool SaveLayerSubset(const Layer<VoxelType>& layer,
  } // namespace io
  } // namespace voxblox
  -#endif // VOXBLOX_CORE_IO_LAYER_IO_INL_H_
  +#endif // VOXBLOX_IO_LAYER_IO_INL_H_
  