undefined method `normalize_item' for class `Class' (NameError)

Try to `$ rails g sidekiq:superworker:install` and get
```bash
/home/sergey/.rvm/gems/ruby-2.0.0-p247/gems/sidekiq-superworker-0.1.2/lib/sidekiq/client_ext.rb:5:in `alias_method': undefined method `normalize_item' for class `Class' (NameError)
	from /home/sergey/.rvm/gems/ruby-2.0.0-p247/gems/sidekiq-superworker-0.1.2/lib/sidekiq/client_ext.rb:5:in `singleton class'
	from /home/sergey/.rvm/gems/ruby-2.0.0-p247/gems/sidekiq-superworker-0.1.2/lib/sidekiq/client_ext.rb:4:in `<class:Client>'
	from /home/sergey/.rvm/gems/ruby-2.0.0-p247/gems/sidekiq-superworker-0.1.2/lib/sidekiq/client_ext.rb:3:in `<module:Sidekiq>'
	from /home/sergey/.rvm/gems/ruby-2.0.0-p247/gems/sidekiq-superworker-0.1.2/lib/sidekiq/client_ext.rb:2:in `<top (required)>'
	from /home/sergey/.rvm/gems/ruby-2.0.0-p247/gems/activesupport-3.2.15/lib/active_support/dependencies.rb:251:in `require'
	from /home/sergey/.rvm/gems/ruby-2.0.0-p247/gems/activesupport-3.2.15/lib/active_support/dependencies.rb:251:in `block in require'
	from /home/sergey/.rvm/gems/ruby-2.0.0-p247/gems/activesupport-3.2.15/lib/active_support/dependencies.rb:236:in `load_dependency'
	from /home/sergey/.rvm/gems/ruby-2.0.0-p247/gems/activesupport-3.2.15/lib/active_support/dependencies.rb:251:in `require'
	from /home/sergey/.rvm/gems/ruby-2.0.0-p247/gems/sidekiq-superworker-0.1.2/lib/sidekiq/superworker.rb:5:in `<top (required)>'
	from /home/sergey/.rvm/gems/ruby-2.0.0-p247/gems/activesupport-3.2.15/lib/active_support/dependencies.rb:251:in `require'
	from /home/sergey/.rvm/gems/ruby-2.0.0-p247/gems/activesupport-3.2.15/lib/active_support/dependencies.rb:251:in `block in require'
	from /home/sergey/.rvm/gems/ruby-2.0.0-p247/gems/activesupport-3.2.15/lib/active_support/dependencies.rb:236:in `load_dependency'
	from /home/sergey/.rvm/gems/ruby-2.0.0-p247/gems/activesupport-3.2.15/lib/active_support/dependencies.rb:251:in `require'
	from /home/sergey/.rvm/gems/ruby-2.0.0-p247/gems/sidekiq-superworker-0.1.2/lib/sidekiq-superworker.rb:1:in `<top (required)>'
	from /home/sergey/.rvm/gems/ruby-2.0.0-p247/gems/bundler-1.3.5/lib/bundler/runtime.rb:72:in `require'
	from /home/sergey/.rvm/gems/ruby-2.0.0-p247/gems/bundler-1.3.5/lib/bundler/runtime.rb:72:in `block (2 levels) in require'
	from /home/sergey/.rvm/gems/ruby-2.0.0-p247/gems/bundler-1.3.5/lib/bundler/runtime.rb:70:in `each'
	from /home/sergey/.rvm/gems/ruby-2.0.0-p247/gems/bundler-1.3.5/lib/bundler/runtime.rb:70:in `block in require'
	from /home/sergey/.rvm/gems/ruby-2.0.0-p247/gems/bundler-1.3.5/lib/bundler/runtime.rb:59:in `each'
	from /home/sergey/.rvm/gems/ruby-2.0.0-p247/gems/bundler-1.3.5/lib/bundler/runtime.rb:59:in `require'
	from /home/sergey/.rvm/gems/ruby-2.0.0-p247/gems/bundler-1.3.5/lib/bundler.rb:132:in `require'
	from /home/sergey/src/trackcha/config/application.rb:7:in `<top (required)>'
	from /home/sergey/.rvm/gems/ruby-2.0.0-p247/gems/railties-3.2.15/lib/rails/commands.rb:24:in `require'
	from /home/sergey/.rvm/gems/ruby-2.0.0-p247/gems/railties-3.2.15/lib/rails/commands.rb:24:in `<top (required)>'
	from script/rails:6:in `require'
	from script/rails:6:in `<main>'

```