fix parameters' name in yolo_video.py

[yush1ga]

This PR fixes #220.

Some parameters in yolo_video.py don't work.
I fix following parameters.

• --model to --model-path
• --anchors to --anchors-path
• --classes to --classes-path

[tuanzhangCS]

I think it might be better to add code:
dest='model_path'
dest='anchors_path'
dest='classes_path'

[hwchase17]

i would update readme as well