Remove `thisArg` from non-nativesque operators

[benlesh]

Per discussion here #787, we will remove the thisArg arguments from all operators that aren't meant to mirror something in native JavaScript.

So really, only map, filter, reduce and forEach should have thisArgs.

Furthermore, the internal bind helper introduces a closure and should probably be removed in favor of using apply or call directly within those operators, or it should be otherwise refactored to not use closures.

[benjamingr]

+1 I think this is important for consistency.

Just adding that the following also need a thisArg: some find findIndex and every