adding examples to Hash#deep_merge method

activesupport/lib/active_support/core_ext/hash/deep_merge.rb

 class Hash
   # Returns a new hash with +self+ and +other_hash+ merged recursively.
+  #
+  #   h1 = {x: {y: [4,5,6]}, z: [7,8,9]}
+  #   h2 = {x: {y: [7,8,9]}, z: "xyz"}
+  #
+  #   h1.deep_merge(h2) #=> {:x => {:y => [7, 8, 9]}, :z => "xyz"}
+  #   h2.deep_merge(h1) #=> {:x => {:y => [4, 5, 6]}, :z => [7, 8, 9]}
   def deep_merge(other_hash)
     dup.deep_merge!(other_hash)
   end
 
-  # Returns a new hash with +self+ and +other_hash+ merged recursively.
-  # Modifies the receiver in place.
+  # Same as +deep_merge+, but modifies +self+
   def deep_merge!(other_hash)
     other_hash.each_pair do |k,v|
       tv = self[k]