version flag in `extractPage` breaks entire executable

[RoyRin]

Running extractPage is broken:

extractPage "Person"
Traceback (most recent call last):
  ..../bin/extractPage", line 8, in <module>
    sys.exit(main())
  File "....wikiextractor/extractPage.py", line 110, in main
    version='%(prog)s ' + version,
NameError: name 'version' is not defined

Fix : remove line 111 from ExtractPage : https://github.com/attardi/wikiextractor/blob/master/wikiextractor/extractPage.py#L111