change unicorn_config_path variable
Merge pull request #26 from lxxdn/use_unicorn_rb

make possible to use unicorn.rb config file
fix "test" method not cd "current_path"

The "test" method won't cd current_path, if pid is set as a relative path, the "test" method will allways return false. Ref: https://github.com/capistrano/sshkit/issues/23