[Breaking change] rename `more()` to something more explicit.

[Carreau]

See #124 and #126, the name more(), is confusing as it indicate that we want to keep iterating over buckets/records whatever even if they all will be empty. Maybe rename to something like more_with_zero_count, or more_empty ? Though this does not convey that all the subsequent one will be empty.

[Carreau]

I'm also unsure if we can do it in a smooth backward compatible manner?

pub trait PickyIterator<T: Counter> {
    ...

    // call more if defined (backward compatibility), 
    #[allow(deprecated)]
    fn more_with_zero_count(&mut self, index_to_pick: usize) -> bool {
        self.more(index_to_pick)
    }

    // provide a default impl for implementation that have already renamed more to
    // more_with_zero_count.
    #[deprecated(...)]
    fn more(&mut self, index_to_pick: usize) -> bool {
        self.more_with_zero_count(index_to_pick)
    }
}

It's a bit dumb as the default impl obviously have infinite recursion, but this make it easy for any implementer of PickyIterator to be supported both with the old and the new name until the old name get removed.

[jonhoo]

I'm just going to leave this open until the next time we do a breaking release :)