Added respond_to_missing? to Item

If you try to call a getter of a key that is not in the data hash, you
will get a NoMethodError instead of a KeyError.

Item now responds correctly if asked if it respond_to?(:getter).  This
was breaking in Rails when you use Object#try

lib/cartman/item.rb

@@ -46,16 +46,22 @@ def cache_key
     end
 
     def method_missing(method, *args, &block)
-      if method.to_s =~ /=\z/
+      if method.to_s.end_with?("=")
         redis.hset _key, method[0..-2], args[0].to_s
         @data.store(method[0..-2].to_sym, args[0].to_s)
         version = touch
         @data.store(:_version, version)
-      else
+      elsif @data.keys.include?(method)
         @data.fetch(method)
+      else
+        super
       end
     end
 
+    def respond_to_missing?(method, include_private = false)
+      method.to_s.end_with?("=") || @data.keys.include?(method) || super
+    end
+
     private
 
     def redis

spec/item_spec.rb

@@ -28,6 +28,15 @@
       it "should touch the item and cart" do
         expect{item.quantity = 4}.to change{item._version}.by(1)
       end
+
+      it "should raise NoMethodError if you use a getter that there isn't a key for" do
+        expect{ item.weight }.to raise_error(NoMethodError)
+      end
+
+      it "should respond_to the getters and setters" do
+        expect(item.respond_to?(:name)).to be true
+        expect(item.respond_to?(:name=)).to be true
+      end
     end
 
     describe "#cost" do