don't validate Application.argv type

it was wrong anyway

closes  #4256

IPython/config/application.py

@@ -144,7 +144,7 b' class Application(SingletonConfigurable):'
     version = Unicode(u'0.0')
     
     # the argv used to initialize the application
-    argv = List(Unicode)
+    argv = List()
 
     # The log level for the application
     log_level = Enum((0,10,20,30,40,50,'DEBUG','INFO','WARN','ERROR','CRITICAL'),