follow android project changes

android-samples/WebViewDemo/Rakefile

@@ -5,7 +5,6 @@ require 'motion/project/template/android'
 Motion::Project::App.setup do |app|
   # Use `rake config' to see complete project settings.
   app.name = 'WebViewDemo'
-  app.main_activity = 'WebViewDemo'
   app.api_version = '18' 
   app.sdk_path = File.expand_path('~/src/android-sdk-macosx')
   app.ndk_path = File.expand_path('~/src/android-ndk-r9d')

android-samples/WebViewDemo/app/WebViewDemo.rb

@@ -1,4 +1,4 @@
-class WebViewDemo < Android::App::Activity
+class MainActivity < Android::App::Activity
   def onCreate(savedInstanceState)
     super
     @handler = Android::Os::Handler.new