fix calib_K using roi info,

Some robots, for example Baxter publishes camera_info with roi
```
        $ rostopic echo -n 1 /cameras/right_hand_camera/camera_info
        header: 
          seq: 2468773
          stamp: 
            secs: 1416402182
            nsecs: 127162000
          frame_id: /right_hand_camera
        height: 400
        width: 640
        distortion_model: plumb_bob
        D: [0.0153369206277, -0.0432553402055, -0.00118657118488,
        -0.00147661359656, 0.00896220693898]
        K: [403.911583563, 0.0, 631.065444573, 0.0, 403.911583563,
        375.688877091, 0.0, 0.0, 1.0]
        R: [1.0, 0.0, 0.0, 0.0, 1.0, 0.0, 0.0, 0.0, 1.0]
        P: [403.911583563, 0.0, 311.06544457300004, 0.0, 0.0,
        403.911583563, 175.688877091, 0.0, 0.0, 0.0, 1.0, 0.0]
        binning_x: 1
        binning_y: 1
        roi: 
          x_offset: 320
          y_offset: 200
          height: 400
          width: 640
          do_rectify: False

```
so we need to consider roi into intrinsic camera parameters.
see https://github.com/ros-perception/vision_opencv/blob/groovy-devel/image_geometry/src/pinhole_camera_model.cpp#L137