Update deploying_on_ubuntu.textile

Update set :deploy_to to reference application not application_name
Update config/unicorn.rb to be consistent

This commit updates the naming of the pid in config/unicorn.rb to be
consistent with the pid naming that comes later in the config/deploy.rb
file.
Merge pull request #93 from MettaAudio/patch-1

Update deploying_on_ubuntu.textile