Add devise_ldap_authenticatable gem, update bundle
Ran 'rails generate devise_ldap_authenticatable:install --advanced'

Also added config.secret_key to devise initializer since above was
unhappy till I did so.
New file from devise_ldap_authenticatable:install generator
Will just leave an example LDAP config in here; git-ignoring the real one
LDAP schema localization; disallow password change attempts
Ignoring ldap.yml so it can have local info like IP addrs