*   Removed need to put nsync/public on C include path when building custom
        ops.
    *   Add `tf.image.psnr`, `tf.image.ssim`, `tf.image.ssim_multiscale`,
        `tf.image.image_gradients`, `tf.image.sobel_edges`.
    *   Add links to https://js.tensorflow.org.
    *   Fix non-uniformity of orthogonal matrices.
    *   Fix bug where multi-image Estimator eval summaries were not displayed
        correctly.