Implement #reverse and implement Iterator to List

[moba1]

Abstract

add #reverse method and implmenent Iterator to List.
#reverse method returns reversed value.

Example

#reverse

List[1,2,3].reverse == List[3,2,1]
# for empty list, return empty list
List[].reverse == List[]
# for list which has one element, return same list
List[1].reverse == List[1]

[alex-lairan]

Some specs missing, I created a pull request to this branch :)

#42

[moba1]

@alex-lairan merged #42

[alex-lairan]

So #41 merged :)