- Move `Slice` -> `slice::Choose`, `EmptySlice` -> `slice::Empty`
- Rename trait `DistString` -> `SampleString`
- Rename `DistIter` -> `Iter`, `DistMap` -> `Map`
- Move `{Weight, WeightError, WeightedIndex}` -> `weighted::{Weight,
Error, WeightedIndex}`
- Move `weighted_alias::{AliasableWeight, WeightedAliasIndex}` ->
`weighted::{..}`
- Move `weighted_tree::WeightedTreeIndex` ->
`weighted::WeightedTreeIndex`