Change default formatter for Rails for better logging of exceptions.

Default Rails Formatter logs messages using

```ruby
 "#{String === msg ? msg : msg.inspect}\n"
 ```

 This is painful when logging Exceptions in descriptive fashion , which ruby's default logger does with-

  ```ruby

      case msg
      when ::String
        msg
      when ::Exception
        "#{ msg.message } (#{ msg.class })\n" <<
          (msg.backtrace || []).join("\n")
      else
        msg.inspect
      end

```

lets use this in case for default formatting.

Handles cases for `ActiveSupport::Logger` and deprecated `ActiveSupport::BufferedLogger` for Applications before Rails 4.0