Ability to set commands on the model's main hash

[Radagaisus]

• Ability to set commands on the model's main hash e.g. expire, ttl, etc.
• The main hash stores the @str and @num attributes of the model.
• We'll need a way to reference it. Options:
  • User(id).some_string_attribute.expire() - will expire the entire hash
  • User(id).main.expire() - use mainor another name to access the hash
  • User(id).expire() - add it directly to the model, though expire() here will only expire the hash and not all the model keys. It's possible for us to expire most of the model keys, but not dynamic keys.
  • User(id).command() - a slightly nicer @_commands.push []