Replace Faraday::Response::Middleware with Faraday::Middleware

lib/librato/metrics/connection.rb

@@ -44,7 +44,7 @@ def transport
         end.tap do |transport|
           transport.headers[:user_agent] = user_agent
           transport.headers[:content_type] = 'application/json'
-          transport.basic_auth @client.email, @client.api_key
+          transport.set_basic_auth @client.email, @client.api_key
         end
       end
 

lib/librato/metrics/middleware/count_requests.rb

@@ -2,7 +2,7 @@ module Librato
   module Metrics
     module Middleware
 
-      class CountRequests < Faraday::Response::Middleware
+      class CountRequests < Faraday::Middleware
         @total_requests = 0
 
         class << self

lib/librato/metrics/middleware/expects_status.rb

@@ -2,7 +2,7 @@ module Librato
   module Metrics
     module Middleware
 
-      class ExpectsStatus < Faraday::Response::Middleware
+      class ExpectsStatus < Faraday::Middleware
 
         def on_complete(env)
           sanitized = sanitize_request(env)

lib/librato/metrics/middleware/request_body.rb

@@ -2,7 +2,7 @@ module Librato
   module Metrics
     module Middleware
 
-      class RequestBody < Faraday::Response::Middleware
+      class RequestBody < Faraday::Middleware
 
         def call(env)
           # duplicate request body so it is preserved through request