Update Middleware section in README
Middleware section referenced Twitter::Response::RaiseClientError which no longer exists. Updated to reference Twitter::Response::RaiseError instead.
|@@ -267,7 +267,7 @@ The Faraday middleware stack is fully configurable and is exposed as a|
|`Faraday::Builder` object. You can modify the default middleware in-place:|
|-Twitter.middleware.insert_after Twitter::Response::RaiseClientError, CustomMiddleware|
|+Twitter.middleware.insert_after Twitter::Response::RaiseError, CustomMiddleware|
|A custom adapter may be set as part of a custom middleware stack:|