rubyzip "~>0.9.1" -> "~> 1.0"

With the changes from this merge request, rodf works with rubyzip 1.0

Motivation: My tests broke with the latest Firefox version (26), to make them work again I need to upgrade the selenium-webdriver gem to version 2.39.0 which requires rubyzip "~> 1.0"

All the specs are passing.