Support for encrypting a data bag item
Add data_bag:encrypted:create task
Support decrypting a data bag item
Refactor encrypted data bag creation

Move the logic for creating an encrypted data bag 
from the task to the DSL method #create_encrypted_data_bag_item
Method #load_data_bag decrypts encrypted items
Replace 'puts' output with Capistrano::CLI.ui.say
Update README.md with encrypted data bag information
Bump gem version and add CHANGELOG.md