Update changelog

Author: davidpdrsn

juniper/CHANGELOG.md

@@ -12,6 +12,7 @@
   The DirectiveLocation::InlineFragment had an invalid literal value,
   which broke third party tools like apollo cli.
 - The return type of `value::object::Object::iter/iter_mut` has changed to `impl Iter` [#312](https://github.com/graphql-rust/juniper/pull/312)
+- Add `GraphQLRequest::operation_name` [#353](https://github.com/graphql-rust/juniper/pull/353)
 
 # [0.11.1] 2018-12-19