Add `drop`, `dropRight`, `dropRightWhile`, `dropWhile`, `take`, `takeRight`, `takeRightWhile`, `takeWhile`, `negate`, `baseValues`, `valuesIn`, `baseFor`, `baseForRight`, `keysIn`, `kebabCase`, `pad`, `padLeft`, `padRight`, `repeat`, `snakeCase`, `startsWith`, `escapeRegExp`, `createCompounder`, `createPad`, `deburrLetter`, and `truncate`.
Remove `createIterator` and `iteratorTemplate`.
Tweak doc notes and rename `callback` vars to `predicate` where appropriate.
Remove `_.isObject` dep from `_.merge` and ensure `_.assign` and `_.defaults` don't error when `object` is `null` or `undefined` and source objects are provided.
Ensure `_.intersection` handles non-array secondary values correctly.
Doc tweaks in `functions`. [ci skip]
Add new methods to categories and make use of them in methods.