Update all pubspecs to work with the latest version of pub and Flutter (#2382)

* Migrated all plugins to the new [plugin platforms manifest](https://flutter.dev/docs/development/packages-and-plugins/developing-packages#plugin-platforms)
* Removed `author:` and `authors:` fields from all pubspecs as the fields are deprecated, moved author names from various plugins to the repository's AUTHORS file.
diff --git a/packages/webview_flutter/pubspec.yaml b/packages/webview_flutter/pubspec.yaml
index 236d591..ea2ea5f 100644
--- a/packages/webview_flutter/pubspec.yaml
+++ b/packages/webview_flutter/pubspec.yaml
@@ -1,12 +1,11 @@
 name: webview_flutter
 description: A Flutter plugin that provides a WebView widget on Android and iOS.
-version: 0.3.17
-author: Flutter Team <flutter-dev@googlegroups.com>
+version: 0.3.18
 homepage: https://github.com/flutter/plugins/tree/master/packages/webview_flutter
 
 environment:
   sdk: ">=2.0.0-dev.68.0 <3.0.0"
-  flutter: ">=1.9.1+hotfix.5 <2.0.0"
+  flutter: ">=1.10.0 <2.0.0"
 
 dependencies:
   flutter:
@@ -20,6 +19,9 @@
 
 flutter:
   plugin:
-    androidPackage: io.flutter.plugins.webviewflutter
-    iosPrefix: FLT
-    pluginClass: WebViewFlutterPlugin
+    platforms:
+      android:
+        package: io.flutter.plugins.webviewflutter
+        pluginClass: WebViewFlutterPlugin
+      ios:
+        pluginClass: FLTWebViewFlutterPlugin