Remove code duplication between deploy:migrate and data:rebuild
BUG In newer versions of ruby the [] evaluates to ascii, failing here.
API Refactor capistrano roles to be requested from cap commands

The CapistranoDeploymentBackend will now reinforce the use of roles, and
scripts have been refactored to work in tandem, only relying on :once
and :except where needed.
Merge pull request #55 from mateusz/ha-data

Refactor capistrano roles to be requested from cap commands everywhere.