Add specs for Semaphore #acquire/#try_acquire with zero permits
Add specs for Semaphore #acquire/#try_acquire with zero permits

hobodave/concurrent-ruby,lucasallan/concurrent-ruby,hobodave/concurrent-ruby,hobodave/concurrent-ruby,hobodave/concurrent-ruby,lucasallan/concurrent-ruby,lucasallan/concurrent-ruby,lucasallan/concurrent-ruby,lucasallan/concurrent-ruby