Miscellaneous fixes and tests

- Rename `repeat` to `repeated` since we have now have a `repeat` in Base (fixes #7)
- Also avoid shadowing `count` and `take` from Base
- Make method signatures more specific where possible, since these names could be used elsewhere
- Fix `partition` method to return a tuple instead of a cell array, and fix some issues with the examples provided
- Add tests

If any of these changes are contentious, I'm happy to break this out into multiple PRs, but I don't think they should be.