Convert all UK spelling to US (#2138)

* all the ise

* forgot a misspelling

* a few more replacements

* bump impl

* rollback and fixes

* bump impl again

* Add aliases for RPC

* Update on_demand.rs

substrate/core/sr-std/build.rs

@@ -3,7 +3,7 @@
 use rustc_version::{version, version_meta, Channel};
 
 fn main() {
-	// Assert we haven't travelled back in time
+	// Assert we haven't traveled back in time
 	assert!(version().unwrap().major >= 1);
 
 	// Set cfg flags depending on release channel