explicitly require "onelogin/ruby-saml/logging" 

so that the developer may do:

```Ruby
require 'onelogin/ruby-saml/authrequest'
```
instead of
```Ruby
require 'onelogin/ruby-saml'
```
or
```Ruby
require 'onelogin/ruby-saml/authrequest'
require 'onelogin/ruby-saml/logging'
```