Added config_dir getter/setter
slightly improved config class, making config dir configurable
Added basic 'configs' command to manage available configurations

* cifrado configs

  Will print all the configurations available in ~/.config/cifrado,
  using the config sort name. That is, it will strip the path plus
  cifradorc from the filename.

  Example:

    $ cifrado configs
    rackspace
    bvox.demo
    bvox
    demo.admin
    bvox.integration
    bvox.demo2
    rbel
    demo

* cifrado configs --current: will print the current configuration
  (~/.config/cifrado/cifradorc), concealing the password.

* cifrado configs --print <short name>: will print the configuration
  matching <short name>, concealing the password.

  Example:

    $ cifrado configs --print rackspace
    :username: user
    :password:
    :auth_url: https://identity.api.rackspacecloud.com/v2.0/tokens
    :secure_random: XXXXXXXXXXXXXXXXXXXXXXXXXXXXX
    :region: DFW

  Prints the config available in ~/.config/cifrado/cifradorc.rackspace
Code cleanup. Use different config and cache dirs while testing