Fix storing changes in WikiPage for Python3

[eseifert]

WikiPage.store() method should call str.encode() after replacing newline characters. Otherwise, under Python 3 it will fail with

TypeError: 'str' does not support the buffer interface

[mblayman]

@eseifert thank you for your contribution!

I noticed that these lines don't have any test coverage. Would you be able to write a test for this? It would help prove that this works on Python 2 and Python 3.

Also, feel free to add yourself to the AUTHORS file.

Let me know if you have any questions. Thanks!

[mblayman]

I can't prove that this doesn't break Python 2 without some tests. The project is getting very light maintenance from me so I'm afraid I'll have to close this unless it can be verified for Python 2 and 3.