Macro to represent a type that can be converted either From
or Into
the given types
This crate only works on the nightly version of Rust
```rust use oneof::oneof;
// either u32
or char
let x: oneof!(u32, char) = 42.into();
asserteq!(Some(42u32), x.into());
assert_eq!(Option::
// some type of integer
let x: oneof!(i8, i16, i32, i64, u8, u16, u32, u64) = 42.into();
asserteq!(Option::
See CHANGELOG.md