Revert "New password default minimum length is now 8"

This reverts commit 2950434.
It is backwards incompatible, we need a better migration plan.

lib/devise.rb

@@ -91,7 +91,7 @@ module Strategies
 
   # Range validation for password length
   mattr_accessor :password_length
-  @@password_length = 6..128
+  @@password_length = 8..128
 
   # The time the user will be remembered without asking for credentials again.
   mattr_accessor :remember_for

lib/generators/templates/devise.rb

@@ -122,7 +122,7 @@
 
   # ==> Configuration for :validatable
   # Range for password length. Default is 8..128.
-  config.password_length = 8..128
+  # config.password_length = 8..128
 
   # Email regex used to validate email formats. It simply asserts that
   # an one (and only one) @ exists in the given string. This is mainly

test/models/validatable_test.rb

@@ -76,10 +76,10 @@ class ValidatableTest < ActiveSupport::TestCase
     assert_equal 'doesn\'t match confirmation', user.errors[:password].join
   end
 
-  test 'should require a password with minimum of 6 characters' do
-    user = new_user(:password => '12345', :password_confirmation => '12345')
+  test 'should require a password with minimum of 8 characters' do
+    user = new_user(:password => '1234567', :password_confirmation => '1234567')
     assert user.invalid?
-    assert_equal 'is too short (minimum is 6 characters)', user.errors[:password].join
+    assert_equal 'is too short (minimum is 8 characters)', user.errors[:password].join
   end
 
   test 'should require a password with maximum of 128 characters long' do