Fix scripts in tool/ to work with Dart 2 (#225)

Fix scripts in tool/ to work with Dart 2
diff --git a/lib/src/emojis.dart b/lib/src/emojis.dart
index cc3e0d6..c7e9bce 100644
--- a/lib/src/emojis.dart
+++ b/lib/src/emojis.dart
@@ -2,7 +2,7 @@
 //
 // This file was generated from emojilib's emoji data file:
 // https://github.com/muan/emojilib/raw/master/emojis.json
-// at 2017-12-30 08:59:02.241410 by the script, tool/update_emojis.dart.
+// at 2018-07-02 15:07:49.422933 by the script, tool/update_emojis.dart.
 
 const emojis = const <String, String>{
   'grinning': '😀',
@@ -624,6 +624,8 @@
   'woman_playing_handball': '🤾‍♀️',
   'man_playing_handball': '🤾‍♂️',
   'ice_skate': '⛸',
+  'curling_stone': '🥌',
+  'sled': '🛷',
   'bow_and_arrow': '🏹',
   'fishing_pole_and_fish': '🎣',
   'boxing_glove': '🥊',
@@ -720,6 +722,7 @@
   'metro': '🚇',
   'tram': '🚊',
   'station': '🚉',
+  'flying_saucer': '🛸',
   'helicopter': '🚁',
   'small_airplane': '🛩',
   'airplane': '✈️',
@@ -1488,6 +1491,9 @@
   'ukraine': '🇺🇦',
   'united_arab_emirates': '🇦🇪',
   'uk': '🇬🇧',
+  'england': '🏴󠁧󠁢󠁥󠁮󠁧󠁿',
+  'scotland': '🏴󠁧󠁢󠁳󠁣󠁴󠁿',
+  'wales': '🏴󠁧󠁢󠁷󠁬󠁳󠁿',
   'us': '🇺🇸',
   'us_virgin_islands': '🇻🇮',
   'uruguay': '🇺🇾',
diff --git a/test/blns.dart b/test/blns.dart
index 7c3a14b..f515658 100644
--- a/test/blns.dart
+++ b/test/blns.dart
@@ -2,7 +2,7 @@
 //
 // This file was generated from big-list-of-naughty-strings's JSON file:
 // https://github.com/minimaxir/big-list-of-naughty-strings/raw/master/blns.json
-// at 2018-04-11 08:45:24.766983 by the script, tool/update_blns.dart.
+// at 2018-07-02 12:53:34.521084 by the script, tool/update_blns.dart.
 
 const blns = const <String>[
   '',
diff --git a/tool/update_blns.dart b/tool/update_blns.dart
index 7e23fd7..744d87f 100644
--- a/tool/update_blns.dart
+++ b/tool/update_blns.dart
@@ -12,8 +12,8 @@
   try {
     var request = await client.getUrl(Uri.parse(_blnsJsonRawUrl));
     var response = await request.close();
-    json = jsonDecode(await response.transform(utf8.decoder).join(''))
-        as List<String>;
+    json = (jsonDecode(await response.transform(utf8.decoder).join('')) as List)
+        .cast<String>();
   } finally {
     client.close();
   }
diff --git a/tool/update_emojis.dart b/tool/update_emojis.dart
index beffc98..fa07c0a 100644
--- a/tool/update_emojis.dart
+++ b/tool/update_emojis.dart
@@ -11,7 +11,8 @@
   var request = await client.getUrl(Uri.parse(_emojisJsonRawUrl));
   var response = await request.close();
   var json = jsonDecode(await response.transform(utf8.decoder).join(''))
-      as Map<String, Map<String, dynamic>>;
+      .map((alias, info) => new MapEntry(alias, info.cast<String, dynamic>()))
+      .cast<String, Map<String, dynamic>>();
   var emojisContent = new StringBuffer('''
 // GENERATED FILE. DO NOT EDIT.
 //