Load unknown library.

  $ antigen-use unknown
  Antigen currently supports only following libraries:
   * oh-my-zsh
   * prezto
  [1]

# Fixme: loading prezto or oh-my-zsh library breaks all the tests.
# 
# Load prezto library.
# 
#   $ antigen-use prezto &> /dev/null
#   $ antigen-bundle git &> /dev/null
# 
# Load oh-my-zsh library.
#  
#   $ antigen-use oh-my-zsh &> /dev/null
#   $ antigen-bundle git &> /dev/null