Fixing a bug introduced in newer versions of Asterisk that broke inte…

…rruptible_play(). The method is now implemented with "STREAM FILE" instead of "EXEC BACKGROUND".

See the Adhearsion mailing list thread here: http://groups.google.com/group/adhearsion/browse_thread/thread/7e6c2687189dcb45

And the Asterisk mailing list thread here: https://issues.asterisk.org/view.php?id=15750

lib/adhearsion/voip/asterisk/commands.rb

@@ -751,7 +751,7 @@ def duration_of
         #
         def interruptible_play(*files)
           files.flatten.each do |file|
-            result = result_digit_from raw_response("EXEC BACKGROUND #{file}")
+            result = result_digit_from raw_response("STREAM FILE #{file} 1234567890*#")
             return result if result != 0.chr
           end
           nil