Refactor methods in html node to avoid injects.

Signed-off-by: Santiago Pastorino <santiago@wyeworks.com>

actionpack/lib/action_controller/vendor/html-scanner/html/node.rb

@@ -38,18 +38,14 @@ def initialize(hash)
     private
 
       def keys_to_strings(hash)
-        hash.keys.inject({}) do |h,k|
-          h[k.to_s] = hash[k]
-          h
-        end
+        Hash[hash.keys.map {|k| [k.to_s, hash[k]]}]
       end
 
       def keys_to_symbols(hash)
-        hash.keys.inject({}) do |h,k|
+        Hash[hash.keys.map do |k|
           raise "illegal key #{k.inspect}" unless k.respond_to?(:to_sym)
-          h[k.to_sym] = hash[k]
-          h
-        end
+          [k.to_sym, hash[k]]
+        end]
       end
   end