Speed Improvement using multi-threading in Human detection exercise

[Gaurav561]

Implementation of multi-threading for faster camera/video frame access.

[aditi25srivastava]

Hi! I would like to work on this issue. Please assign it to me.

[jmplaza]

@codezerro @dpascualhe is this issue meaningful with the recent update of that exercise?

[dpascualhe]

@jmplaza doesn't make much sense as it is working smoothly. Also, any issues with cam access would be common to any computer vision exercise, not only human detection.