Merge branch 'fix-rubyzip-require' into 'master'

[master] Fix requiring the rubyzip Gem

See merge request gitlab/gitlabhq!2876

Gemfile

@@ -57,7 +57,7 @@ gem 'u2f', '~> 0.2.1'
 
 # GitLab Pages
 gem 'validates_hostname', '~> 1.0.6'
-gem 'rubyzip', '~> 1.2.2'
+gem 'rubyzip', '~> 1.2.2', require: 'zip'
 
 # Browser detection
 gem 'browser', '~> 2.5'