STITCH_IMAGES - Given a set of images with overlapping regions,
                automatically compute a panorama image.

Usage:    [result_img, H, num_inliers, residual] ...
              = stitch_images (images, sift_r, harris_r, ...
              harris_thresh, harris_sigma, num_putative_matches, ransac_n)

Usage example:
          stitch_images(images, 5, 5, 0.03, 1, 100, 4000)

Arguments:
          images                - 1 by n cell array of images.
          sift_r                - radius of the SIFT descriptor.
          harris_r              - radius of the Harris corner detector.
          harris_thresh         - Harris corner detector threshold.
          harris_sigma          - standard deviation of smoothing Gaussian
          num_putative_matches  - number of putative matches to run
                                  RANSAC.
          ransac_n              - number of RANSAC iterations.

Returns:
          result_img    - computed paranoma image.
          H             - n by n cell array of homography matrices.
                          H{i, j} is the homography matrix between images
                          i and j.
          num_inliers   - n by n array of number of inliers. num_inliers{i,
                          j} is the number of inliers between images i and
                          j.
          residual      - n by n array of sum of squared disrances.
                          residual{i, j} is the residual between images i
                          and j.

Dependencies:
          VLFeat        - download at http://www.vlfeat.org/download.html