Merge pull request #34 from Metaswitch/dependabot/cargo/itertools-0.13

Update itertools requirement from 0.12 to 0.13

Author: bossmc

derive/Cargo.toml

@@ -18,7 +18,7 @@ proc-macro = true
 syn = "1.0"
 proc-macro2 = "1.0"
 quote = "1.0"
-itertools = "0.12"
+itertools = "0.13"
 frunk_proc_macro_helpers = "0.1"
 
 [dev-dependencies]