Autolink URLs with nested parentheses.
Remove underscore from conformance tests description.
Allow only one nested level of balanced parentheses.
Test against Ruby 2.0.0 on Travis CI.
Use nokogiri 1.5.10 (1.6 is doesn't support Ruby 1.8).
Merge pull request #100 from twitter/kl_autolink_urls_with_nested_parens

Autolink URLs with nested parentheses.