Correct `enumerable#indexOf` and `enumerable#lastIndexOf`

These should take values to strictly compare against, not functions to
invoke.
Delegate `enumerable#reject` to `enumerable#filter`

This also makes the `arraylike#reject` implementation redundant, so that
was removed as well.
Modify `enumerable#reduce` to correctly handle empty objects
Remove initial value from `enumerable#min` and `enumerable#max`
Refactor `mixins/enumerable` to not clobber existing methods