[doc] #111: Add script to update the copyright year

update_copyright_year.sh

+#!/bin/fish
+
+# Script to update the copyright year in header files
+
+set NEW_YEAR (date +"%Y")
+set OLD_YEAR (math $NEW_YEAR - 1)
+find duniterpy tests examples -type f -name "*.py" | \
+xargs sed -i "s/Copyright  2014-$OLD_YEAR V/Copyright  2014-$NEW_YEAR V/g"