Test::Unit Gemfile needs shoulda as well & Updated copyright year

I've used shoulda-matchers with Rspec with no difficulty, but when I tried to use it yesterday with Test::Unit, it gave me undefined method should when running the tests. The problem was solved when I added gem 'shoulda' to my Gemfile, and the tests work as designed.

I added instructions in the README if using Test::Unit, you should also add shoulda to the Gemfile. 

I also updated the copyright year to 2014.