Fixed the screenshot link to my own

Author: derdennis

README.markdown

@@ -100,6 +100,6 @@ previous type, then the counter will not be restarted.
 [1]: https://github.com/vim-pandoc/vim-markdownfootnotes/
 [2]: http://www.vim.org/scripts/script.php?script_id=431
 [3]: http://www.nickcoleman.org/blog/index.cgi?post=footnotevim%21201102211201%21programming
-[4]: https://raw.github.com/vim-pandoc/vim-markdownfootnotes/master/footnotes.png
+[4]: https://raw.github.com/derdennis/vim-markdownfootnotes/master/footnotes.png
 [5]: http://slipsum.com/
 [6]: https://github.com/tpope/vim-pathogen