install impression-1.4.4 for mongoid

gistfile1.txt

/home/wangyang/.rvm/gems/ruby-1.9.3-p392/gems/impressionist-1.4.4/lib/impressionist/models/active_record/impression.rb:8:in `<top (required)>': uninitialized constant ActiveRecord (NameError)
	from /home/wangyang/.rvm/gems/ruby-1.9.3-p392/gems/impressionist-1.4.4/lib/impressionist/engine.rb:25:in `include_orm'
	from /home/wangyang/.rvm/gems/ruby-1.9.3-p392/gems/impressionist-1.4.4/lib/impressionist/engine.rb:7:in `block in <class:Engine>'
	from /home/wangyang/.rvm/gems/ruby-1.9.3-p392/gems/railties-3.2.13/lib/rails/initializable.rb:30:in `instance_exec'
	from /home/wangyang/.rvm/gems/ruby-1.9.3-p392/gems/railties-3.2.13/lib/rails/initializable.rb:30:in `run'
	from /home/wangyang/.rvm/gems/ruby-1.9.3-p392/gems/railties-3.2.13/lib/rails/initializable.rb:55:in `block in run_initializers'
	from /home/wangyang/.rvm/gems/ruby-1.9.3-p392/gems/railties-3.2.13/lib/rails/initializable.rb:54:in `each'
	from /home/wangyang/.rvm/gems/ruby-1.9.3-p392/gems/railties-3.2.13/lib/rails/initializable.rb:54:in `run_initializers'
	from /home/wangyang/.rvm/gems/ruby-1.9.3-p392/gems/railties-3.2.13/lib/rails/application.rb:136:in `initialize!'
	from /home/wangyang/.rvm/gems/ruby-1.9.3-p392/gems/railties-3.2.13/lib/rails/railtie/configurable.rb:30:in `method_missing'
	from /home/wangyang/Repository/demo/megahealth-rails3/config/environment.rb:5:in `<top (required)>'
	from /home/wangyang/.rvm/gems/ruby-1.9.3-p392/gems/railties-3.2.13/lib/rails/application.rb:103:in `require_environment!'
	from /home/wangyang/.rvm/gems/ruby-1.9.3-p392/gems/railties-3.2.13/lib/rails/commands.rb:25:in `<top (required)>'
	from script/rails:6:in `require'
	from script/rails:6:in `<main>'

I'm experiencing the same issue. Is there something I'm missing? Did you figure anything out?