some advice about sot video demo

[laisimiao]

Hello @MARMOTatZJU @lzx1413 Thanks for your wonderful work and open codes.I have try to use sot video demo(demo/main/video/sot_video.py) and give you some feedback so that you can improve or fix them:

• in line66, it should be ''dump_only" not "dump-only";
• After line157 it should add another line:cv2.waitKey(1) so the track result frame will be showed correctly, otherwise it's just a white window;
• For third demo way(that is, with extracted image files), don't forget to add "-i " params to define object location in initial frame and when use param "--video", don't forget to add quotation marks to path;
• the last is that for test image whose size is less than 128×128, the template can't be displayed on the left-top of current frame. If in future work it had better use proportionate size not fixed size. Above are my advice. Thanks again!

[lzx1413]

Thanks for you suggestions. A PR is welcome with these refinements.