update hello, world sample and remove slider

samples/slider/slider_sample.css

Index: samples/slider/slider_sample.css
diff --git a/samples/slider/slider_sample.css b/samples/slider/slider_sample.css
deleted file mode 100644
index e2b985313b6a7d46aafa4fa4b791e0c7191dea68..0000000000000000000000000000000000000000
--- a/samples/slider/slider_sample.css
+++ /dev/null
@@ -1,70 +0,0 @@
-/* Copyright (c) 2012, the Dart project authors.  Please see the AUTHORS file */
-/* for details. All rights reserved. Use of this source code is governed by a */
-/* BSD-style license that can be found in the LICENSE file. */
-
-body {
-  background-color: #F8F8F8;
-  font-family: 'Open Sans', sans-serif;
-  font-size: 14px;
-  font-weight: normal;
-  line-height: 1.2em;
-  margin: 15px;
-}
-
-p {
-  color: #333;
-}
-
-#container {
-  width: 100%;
-  height: 400px;
-  position: relative;
-  border: 1px solid #ccc;
-  background-color: #fff;
-}
-
-#summary {
-  float: left;
-}
-
-#notes {
-  float: right;
-  width: 120px;
-  text-align: right;
-}
-
-.error {
-  font-style: italic;
-  color: red;
-}
-
-#container2 {
-  width: 100px;
-  height: 100px;
-  position: relative;
-  margin: auto;
-}
-
-#target {
-  width: 100%;
-  height: 100%;
-  position: absolute;
-}
-
-#target figure {
-  display: block;
-  position: absolute;
-  width: 150px;
-  height: 80px;
-  border: 1px solid #333;
-  font-size: 36px;
-  color: #222;
-  background: #3291d8;
-  text-align: center;
-  line-height: 2em;
-}
-
-#message {
-  margin-top: 20px;
-  font-size: 16px;
-}