Modified list::from_vec() to return List<T>
Implemented Items<'a, T> for List<T>
Replaced list::each with iter() in Arenas's Drop impl
Replaced list::each with iter() in get_region
Removed list::foldl() in favor of iter().fold()
Removed list::find() in favor of iter().find()
Removed list::any() in favor of iter().any()
Implemented list::len() based on Container trait
Removed deprecated list::iter() function
Implemented list::is_empty() based on Container trait
Replaced list::has() with list::contains()
Removed deprecated list::each() function
Refactored list::head() to be based on List<T>
Refactored list::tail() to be based on List<T>
Refactored list::append() to be based on List<T>
Replaced list::push() with unshift() based on List<T>