Implement std::error::Error for public Error struct

[nukemberg]

Implementing the std::error::Error trait allows for error forwarding and interoperability with error handling libraries e.g. thiserror.

[nukemberg]

I see that since #![no_std] is used std::error::Error cannot be implemented. Is there any way to make this conditional? e.g. via features?

[VersBinarii]

There is a pull request #13 awaiting to address that.
I will merge it as soon as its rebased. If there is no response from author i will apply that change manually over the weekend.

[VersBinarii]

Closing this with #17