Support std::io::{Read, Write, Seek}

[ikrivosheev]

Hello! Thank you for very useful crate!

Before Rust I wrote in python. Python has its implementation for mmap. In python I can work with mmap like with File
I propose to implement traits std::io::{Read, Write, Seek}. If nobody don't mind, I'm ready to create PR.

[adamreichold]

A memory map provides access to a byte slice &[u8] resp. &mut [u8] which implements Read and Write. If you need Seek, you'll just need to wrap the slice into a Cursor. So Cursor<MmapMut> should already fulfil the requirement of using a memory map like a file?

[RazrFalcon]

Yes, as mentioned about, it should work out of the box.

[ikrivosheev]

@RazrFalcon @adamreichold, thank for the answer! I got it and it works!