Fix PyGI warnings about enums

Fixes

    ** (gtimelog:329385): WARNING **: 15:20:47.851: expected enumeration type void, but got PyGLibOptionArg instead

    ** (gtimelog:329385): WARNING **: 15:20:47.852: expected enumeration type void, but got PyGLibOptionArg instead

    ** (gtimelog:329385): WARNING **: 15:20:47.852: expected enumeration type void, but got PyGLibOptionArg instead

    ** (gtimelog:329385): WARNING **: 15:20:47.852: expected enumeration type void, but got PyGLibOptionArg instead

Closes #249.

src/gtimelog/main.py

@@ -163,7 +163,8 @@ def make_option(long_name, short_name=None, flags=0, arg=GLib.OptionArg.NONE,
     option.long_name = long_name.lstrip('-')
     option.short_name = 0 if not short_name else short_name.lstrip('-')
     option.flags = flags
-    option.arg = arg
+    # Not 100% sure about the int(), but it fixes a warning from PyGI
+    option.arg = int(arg)
     option.arg_data = arg_data
     option.description = description
     option.arg_description = arg_description