Add support for crypto 1.0.0..

lib/src/channel.dart

Index: lib/src/channel.dart
diff --git a/lib/src/channel.dart b/lib/src/channel.dart
index 446eb694a7903d284bf6b507d34505cc0d920dd6..3d1d4929994abe6c91c558b4405d7a34a66a5aa4 100644
--- a/lib/src/channel.dart
+++ b/lib/src/channel.dart
@@ -62,11 +62,9 @@ class WebSocketChannel extends StreamChannelMixin {
   ///
   /// [initial handshake]: https://tools.ietf.org/html/rfc6455#section-4.2.2
   static String signKey(String key) {
-    var hash = new SHA1();
     // We use [codeUnits] here rather than UTF-8-decoding the string because
     // [key] is expected to be base64 encoded, and so will be pure ASCII.
-    hash.add((key + webSocketGUID).codeUnits);
-    return CryptoUtils.bytesToBase64(hash.close());
+    return BASE64.encode(sha1.convert((key + webSocketGUID).codeUnits).bytes);
   }
 
   /// Creates a new WebSocket handling messaging across an existing [channel].