added example of a mock yielding to a block
added example of a mock yielding to a block

alitalia/rspec,mrkn/rspec,dchelimsky/rspec,dchelimsky/rspec-stories,phinze/rspec,dchelimsky/rspec-stories,alitalia/rspec,patmaddox/rspec,patmaddox/rspec,dchelimsky/rspec