Add support for “nokogiri” gem > 1.8 regarding CVE-2019-11068:

Advisory: CVE-2019-11068
Criticality: Unknown
URL: sparklemotion/nokogiri#1892
Title: Nokogiri gem, via libxslt, is affected by improper access control vulnerability
Solution: upgrade to >= 1.10.3

saml.gemspec

@@ -19,7 +19,7 @@ Gem::Specification.new do |s|
   s.add_dependency "activesupport", ">= 4.2"
   s.add_dependency "activemodel", ">= 4.2"
   s.add_dependency "xmlmapper", '~> 0.7.3'
-  s.add_dependency 'nokogiri', '~> 1.8', '>= 1.8.2', '<= 1.8.5'
+  s.add_dependency 'nokogiri', '~> 1.8'
   s.add_dependency "xmldsig", '>= 0.5.1', '< 0.8.0'
   s.add_dependency "xmlenc", '>= 0.6.9', '< 0.8.0'