page on iOS now takes window number

The number can be any int >= 0. Examples:

page 0 # regular app page
page 1 # wifi
page 2 # alerts

Fix #88

Author: bootstraponline

lib/appium_lib/ios/helper.rb

@@ -151,8 +151,8 @@ def fix_space s
 
   # Prints a string of interesting elements to the console.
   # @return [void]
-  def page
-    get_page
+  def page window_number = 0
+    get_page source_window window_number || 0
     nil
   end