Derive enum from try into

Implements From and TryInto for enums with single fields. Also ignores variants with duplicate type definition

```rust use deriveenumfrom_into::{EnumFrom, EnumTryInto};

[derive(EnumFrom, EnumTryInto, PartialEq)]

enum X { A(i32), B(String), C(String), D, E { something: i32 }, F(Box) }

assert_eq!( X::from(54i32), X::A(54i32) );

let nestedx: Result, _> = X::D.tryinto(); asserteq!(nestedx, Err(())); let nestedx: Result, _> = X::F(Box::new(X::D)).tryinto(); asserteq!(nestedx, Ok(Box::new(X::D))); ```