cleanup encode_raw_saml method:

* remove duplication by using local `deflate` method
* remove unnecessary variable assignment

Author: phlipper

lib/onelogin/ruby-saml/saml_message.rb

@@ -59,9 +59,9 @@ def decode_raw_saml(saml)
       end
 
       def encode_raw_saml(saml, settings)
-        saml           = Zlib::Deflate.deflate(saml, 9)[2..-5] if settings.compress_request
-        base64_saml    = Base64.encode64(saml)
-        return CGI.escape(base64_saml)
+        saml = deflate(saml) if settings.compress_request
+
+        CGI.escape(Base64.encode64(saml))
       end
 
       def decode(encoded)