Add destroy method for Link

.gitignore

@@ -12,3 +12,4 @@
 *.o
 *.a
 mkmf.log
+.DS_Store

lib/omise/link.rb

@@ -27,6 +27,10 @@ def reload(attributes = {})
       assign_attributes resource(attributes).get(attributes)
     end
 
+    def destroy(attributes = {})
+      assign_attributes resource(attributes).delete
+    end
+
     def charges(options = {})
       if options.empty?
         list_attribute ChargeList, "charges"

test/fixtures/api.omise.co/links/link_test_55pcclmznvrv9lc7r9s-delete.json

@@ -0,0 +1,6 @@
+{
+  "object": "link",
+  "id": "link_test_55pcclmznvrv9lc7r9s",
+  "livemode": false,
+  "deleted": true
+}

test/omise/test_link.rb

@@ -17,6 +17,13 @@ def test_that_we_can_retrieve_a_link
     assert_equal "link_test_55pcclmznvrv9lc7r9s", @link.id
   end
 
+  def test_that_we_can_destroy_a_link
+    @link.destroy
+
+    assert @link.deleted
+    assert @link.destroyed?
+  end
+
   def test_that_we_can_list_all_links
     links = Omise::Link.list