Update substrate and codec crate aliases (#54)

* Replace substrate crate aliases with actual crate names

* Alias parity-scale-codec to just codec, like in substrate

* Format code

src/frame/contracts.rs

@@ -16,13 +16,12 @@
 
 //! Implements support for the pallet_contracts module.
 
-use parity_scale_codec::Encode;
-
 use crate::frame::{
     balances::Balances,
     system::System,
     Call,
 };
+use codec::Encode;
 
 const MODULE: &str = "Contracts";
 const PUT_CODE: &str = "put_code";