expectations 0.1.0

[Per Nordlöw]

On Sunday, 2 September 2018 at 06:59:20 UTC, Paul Backus wrote:
> expectations is an error-handling library that lets you bundle 
> exceptions together with return values. It is based on Rust's 
> Result<T, E> [1] and C++'s proposed std::expected. [2] If 
> you're not familiar with those, Andrei's NDC Oslo talk, "Expect 
> the Expected" [3], explains the advantages of this approach to 
> error handling in considerable detail.

Incidentally, I've already proposed `Expected` into Phobos 
std.experimental.typecons here

https://github.com/dlang/phobos/pull/6686

Is it ok if I try to merge your effort into this pull request?