Add #[feature(macro_rules)] to enable Macros on newer Rust versions.
Remove checkedcast.rs and switch over to using cast() which has been updated to return an Option.
Make the test module in cryptutil public since its used by other module's tests.
Use explicitly named imports since glob imports are considered experimental.
Merge pull request #1 from DaGenix/update-for-newer-rust

Updates to work on a newer Rust version