Add commander class
Use single quotes instead of double quotes
Move with_secure_pin to Commander::with_pin
Add commander context class
Execute ::with_pin block in a special context
Move command execution to the Commander class
Use dot for method calls
Add context methods #aqhbci and #aqcli
Move popen3 execution into Commander class
Add tests for User::remove
Make Commander::execute return output and status
Clean up spec
Add nokogiri dependency
Add command flag :xml
Add user attributes to initializer
Generalize complain_missing_params
Add User::list method