iterext: A few more extension methods on iterators.

This crate is not likely to ever be published on https://crates.io because it's far more appropriate to attepmt to get these extensions added to itertools. However, I haven't yet made the time to attempt to contribute them there.

A few quick examples from the tests should show what it's about:

```rust use iterext::prelude::*;

[test]

fn testseparate() { for (msg, expect) in &[ ("abc", "abc"), ("zyx", "zyx"), ( "abcdefghijklmnopqrstuvwxyz", "abcde fghij klmno pqrst uvwxy z", ), ( "thequickbrownfoxjumpedoverthelazydog", "thequ ickbr ownfo xjump edove rthel azydo g", ), ( "abcdefghijklmnopqrstuvwxyzabcdefghijklmnopqrstuvwxyz", "abcde fghij klmno pqrst uvwxy zabcd efghi jklmn opqrs tuvwx yz", ), ] { let got: String = msg.chars().separate(' ', 5); asserteq!(&got, expect,); } }

[test]

fn testpaddingchars() { let have = "foo".chars().pad('X', 5).collect::(); assert_eq!(have, "fooXX"); } ```

Provenance

Originally wrote these extensions as part of the textbyte module for my solitaire implementation.