Add Borrowed Deserialization support (#1)

[hamidrezakp]

Hello,
This PR will add a new trait called BorshBorrowedDeserialize which has explicit lifetime.
It's purpose is to efficiently and without allocating new memory, deserialize &[u8] and &str slices.

Changes:

• Add support for str and u8 slice
• Add derive macros for borrowed version of deserializer trait

It would be great if we can have this trait in the main crate.

[hamidrezakp]

I noticed that derive macro needs better handling of life times and we can't use blanket impl.
Therefore have to write explicit impl for each type supported in other trait. will update this PR soon.

Just wanted to hear your feedback on this.
Thank you.