Get rid of icu string functions in favor of native ones.

ebook_converter/startup.py

@@ -104,11 +104,6 @@ if not _run_once:
         except:
             pass
 
-    from ebook_converter.utils.icu import lower as icu_lower, upper as icu_upper
-    builtins.__dict__['icu_lower'] = icu_lower
-    builtins.__dict__['icu_upper'] = icu_upper
-    builtins.__dict__['icu_title'] = lambda s: ' '.join([x.capitalize() for x in s.split(' ')])
-
     def connect_lambda(bound_signal, self, func, **kw):
         import weakref
         r = weakref.ref(self)