checking for expired token as part of authenticated?

Conflicts:
	lib/mkto_rest.rb

Author: erdostom

lib/mkto_rest.rb

@@ -23,7 +23,11 @@ def debug=(bool)
     end
 
     def authenticated?
-      !@token.empty?
+      !@token.empty? && token_valid?
+    end
+
+    def token_valid?
+      return Time.now < @valid_until
     end
 
     # used for testing only