To show all tasks decalred in default config and stages files was missed from the tasks list.
Added default value for :stage and load all default configs. Also added cucumber tests.
This change allows both the `deploy_config_path` and `stage_config_path`
to be moved from the default locations of `config/deploy.rb` and
`config/deploy` respectively. These values __must__ be set in the
`Capfile` prior to `capistrano/setup` being called, for example:
set :deploy_config_path, 'app/config/deploy.rb'
set :stage_config_path, 'app/config/deploy'
# Load DSL and Setup Up Stages
require 'capistrano/setup'
Fixes#610