bump up oath2

Author: Andrew Shatnyy

omniauth-okta.gemspec

@@ -15,7 +15,7 @@ Gem::Specification.new do |s|
   s.files = Dir["{app,config,db,lib}/**/*", "MIT-LICENSE", "Rakefile", "README.md"]
 
   s.add_dependency "omniauth", "~> 1.5"
-  s.add_dependency "omniauth-oauth2", ">= 1.4.0", "< 2.0"
+  s.add_dependency "omniauth-oauth2", ">= 1.6.0", "< 2.0"
 
   s.add_development_dependency "bundler", "~> 1.5"
   s.add_development_dependency "rake"