Add ConvexHull using Graham's Scan

[arnabuchiha]

If Convexhull is not implemented yet, Can I do it?
@KuLi @TangibleDream @Vodkacannon

[arnabuchiha]

I have implemented in pull request #416 . Please review it and merge it .

[stale]

This issue has been automatically marked as stale because it has not had recent activity. It will be closed if no further activity occurs. Thank you for your contributions.

[stale]

Please reopen this issue once you commit the changes requested or make improvements on the code. Thank you for your contributions.