Encode an index of a nibble from a u64 as a u8.

| 4 bits | 4 bits |

| index of nibble | nibble of data |

Usage

```rust use crumb::Crumb;

fn main() { let crumb = Crumb::new(1, 0b11111111).unwrap(); asserteq!(0b11110000u64, crumb.getu64()); // external bits are discarded } ```

Name

A nibble of something is about the size of a crumb or something like that...

Why?

Was doing some research on variable length integers and realized how nicely this fits.

For What?

Not sure!

I don't think there are too many applications for this.