Update to use Vec struct to make it work on latest Rust HEAD.
Merge pull request #16 from utkarshkukreti/use-vec-struct

Update to use Vec struct to make it work on latest Rust HEAD.
Remove all `#![feature(managed_boxes)]`as we're not using them anymore.
Merge pull request #17 from utkarshkukreti/remove-managed-boxes-feature

Remove all `#![feature(managed_boxes)]`as we're not using them anymore.