Fix extra allocation and copy.

[jlennox]

Inside YoloWrapper.Detect(byte[]) there's a costly allocation and copy of the image buffer. This can be prevented by pinning the provided array instead.

There was also Marshal.SizeOf(imageData[0]) which since the supplied buffer is byte[] is an expensive way (has a memory read and Marshal.SizeOf is not cheap/free like sizeof) to get the constant 1.

[zgabi]

@jlennox The previous maintainer of this pachkage left the company, see #143.
I've created a copy from this repository and added this functianlity.
https://github.com/zgabi/Yolo.Net

Also created a nuget package: https://www.nuget.org/packages/Yolo.Net/3.0.6-alpha.1

Feel free to crete PRs on my repository.

[jlennox]

Thanks.