Add document for #319 (#323).
Add document for #319 (#323).

ashigeru/asakusafw,akirakw/asakusafw,cocoatomo/asakusafw,asakusafw/asakusafw,akirakw/asakusafw,cocoatomo/asakusafw,asakusafw/asakusafw,ashigeru/asakusafw