Add explicit requires for things in ActiveSupport that Summer needs, …

…rather than "all" of ActiveSupport.

With AS 3.0, the previous line here  loads the 'barebones' AS, thereby not loading the HWIA class or the try method.
By specifically loading these two files, we should be only loading the ones which are required.

lib/summer.rb

@@ -1,6 +1,7 @@
 require 'socket'
 require 'yaml'
-require 'active_support'
+require 'active_support/hash_with_indifferent_access'
+require 'active_support/core_ext/object/try'
 
 Dir[File.dirname(__FILE__) + '/ext/*.rb'].each { |f| require f }