v0.2.0 - Added bitflags

Added bitflags, so now you can do stuff like this:

use better_enums::{better_enums, flags::TryFromBits};

#[better_enums(bitflags)]
#[repr(u8)]
enum Permission {
    Read = 0b0000_0001,
    Write = 0b0000_0010,
    Execute = 0b0000_0100,
}

let permissions = Permission::Read | Permission::Write;
assert!(permissions.contains(Permission::Read));
assert_eq!(permissions.value(), 0b0000_0011);
assert!(Permission::try_from_bits(0b0000_1000).is_err());

Also changed the layout of the crate, now its easier extendable (if needed in the future)