Use RFC 2396 compatible URI parser for trustroot.

From Ruby 2.2 the default `URI.parse` method uses a new RFC 3986
compatible parser, which will parse most of the “invalid” URLs in the
trustroot test.

Author: Tobias Haagen Michaelsen

lib/openid/trustroot.rb

@@ -178,7 +178,7 @@ def TrustRoot._parse_url(url)
         end
 
         begin
-          parsed = URI::parse(url)
+          parsed = URI::DEFAULT_PARSER.parse(url)
         rescue URI::InvalidURIError
           return nil
         end