Adds a Tasks::Helpers module to encapsulate logic from rake and capistrano tasks.

Because of sharing this helper methods between the db.rake and capistrano.rb the `rake alchemy:db:dump` task can now take the --host option for mysqldump. (Useful for importing sql from an external db server)
Merge pull request #428 from robinboening/master

Adds a Tasks::Helpers module to encapsulate logic from rake and capistrano tasks.