Fix typo in Addressable::Template extract example in README. Fixes #164

I'm not too proud to say I've spend a good part of an hour tracking this one down. Turns out the issue that was confusing in #164 is a simple missing asterisk in the README example pattern.

P.S.: You should perhaps lock the version of RSpec to 2.11, as the >= 2.9 dependency specification in the Gemfile will just install 3.x by default, which doesn't work. But then 2.9 doesn't work either (because of `subject` and `expect` API changes).