Fixed deprecation warning with Faraday

Faraday::Builder is now Faraday::RackBuilder.

Author: joeworkman

lib/bitbucket_rest_api/connection.rb

@@ -75,9 +75,9 @@ def caching?
     def stack(options={}, &block)
       @stack ||= begin
         if block_given?
-          Faraday::Builder.new(&block)
+          Faraday::RackBuilder.new(&block)
         else
-          Faraday::Builder.new(&default_middleware(options))
+          Faraday::RackBuilder.new(&default_middleware(options))
         end
       end
     end