Apply Style/AndOr and Style/Not rubocop rules

The `and` and `or` keywords are not equivalent to `&&` and `||` and its
use is counterintuitive. Here's an example

```
good = true && false # good if false
bad = true and false # bad is true
```

The reason is `and` and `or` are control flow operators. So the code:

```
bad = true and false
```

Is equivalent to:


```
if bad = true
  false
end
```

.rubocop.yml

@@ -367,9 +367,15 @@ Security/JSONLoad:
 Security/YAMLLoad:
   Enabled: true
 
+Style/AndOr:
+  Enabled: true
+
 Style/BlockDelimiters:
   Enabled: true
 
+Style/Not:
+  Enabled: true
+
 Style/PercentLiteralDelimiters:
   Enabled: true
 

config/initializers/devise_security_extension.rb

@@ -62,7 +62,7 @@ module Devise
         if !self.new_record? && !self.encrypted_password_change.nil? && !self.erased?
           dummy = self.class.new
           dummy.encrypted_password = self.encrypted_password_change.first
-          dummy.password_salt = self.password_salt_change.first if self.respond_to? :password_salt_change and not self.password_salt_change.nil?
+          dummy.password_salt = self.password_salt_change.first if self.respond_to?(:password_salt_change) && !self.password_salt_change.nil?
           self.errors.add(:password, :equal_to_current_password) if dummy.valid_password?(self.password)
         end
       end