rb: add utf-8 encoding to all .rb files

Author: andreastt

Rakefile

@@ -709,7 +709,8 @@ namespace :copyright do
         :prefix => "#!/usr/bin/python\n#\n")
     Copyright.Update(
       FileList["rb/**/*.rb"],
-      :style => "#")
+      :style => "#",
+      :prefix => "# encoding: utf-8\n\n")
     Copyright.Update(
         FileList["java/**/*.java"].exclude(
             "java/client/src/org/openqa/selenium/internal/Base64Encoder.java",

rb/lib/selenium-client.rb

@@ -1,3 +1,5 @@
+# encoding: utf-8
+
 # Licensed to the Software Freedom Conservancy (SFC) under one
 # or more contributor license agreements.  See the NOTICE file
 # distributed with this work for additional information