2.3-stable: Gemfile: pin selenium-webdriver version 2.35.1.

selenium-webdriver requires rubyzip 1.0.0.
rubyzip 1.0.0 requires Ruby version >= 1.9.2.

git-svn-id: svn+ssh://rubyforge.org/var/svn/redmine/branches/2.3-stable@12227 e93f8b46-1217-0410-a6f0-8f06a7374b81