Remove unneeded Serde requirements (#1076)

* Remove superfluous serde requirements.

* Try to ensure hash is serde

* Fixups

* Building again

* Attempt to reenable Block (doesn't build)

* Fixes compilation for node cli

* Fixes test compilation

* Fix wasm

* Fix tests

* Remove unneeded changes

* Fix up comments

* Reenable some code

* Compile error when origin misused.

* Remove unnecessary includes of `serde_derive`

* Cleanups

substrate/srml/session/src/lib.rs

@@ -19,10 +19,6 @@
 
 #![cfg_attr(not(feature = "std"), no_std)]
 
-#[cfg(feature = "std")]
-#[macro_use]
-extern crate serde_derive;
-
 extern crate sr_std as rstd;
 
 #[macro_use]