cases: added ICU conformance test Change-Id: I1a9d4dc10b57bbdf362f4f7d13272fe8fde49721 Reviewed-on: https://go-review.googlesource.com/29179 Run-TryBot: Marcel van Lohuizen <mpvl@golang.org> TryBot-Result: Gobot Gobot <gobot@golang.org> Reviewed-by: Nigel Tao <nigeltao@golang.org>