Make lazy `_.drop` test more complex.
Fix _.keysIn for inherited non-enumerable props.
Add test for inherited shadowed props.
Ensure `_.keysIn` skips  inherited`constructor` properties.
Simplify lazy chaining.
Ensure `root` is set correctly when required by a greasemonkey userscript. [closes #759]
Cleanup `_.keysIn`.
Cleanup `_.dropRightWhile` and `_.takeRightWhile`.
Add another [[DontEnum]] test.