add gems
rails generate devise:install
after running `rails generate devise User` and `rails g devise:views`
custom the device view file to adopt the bootstrap 3 theme
after running `rake db:migrate` and `rails generate devise_ldap_authenticatable:install`
ldap yml change
enable ldap_create_user
avoid deprecated warning
enable login via email and Authorizing user with AD
enable login via badge and same the email if exist.