Antigen doesn't do automatic updates like oh-my-zsh. Set up easy auto updating, both of antigen and the bundles loaded in your configuration.
Activate with antigen bundle unixorn/autoupdate-antigen.zshplugin
set ANTIGEN_PLUGIN_UPDATE_DAYS before calling the bundle if you don't want
the default value of 7 days.
set ANTIGEN_SYSTEM_UPDATE_DAYS before calling the bundle if you don't want
the default value of 7 days.
These values must be integers.
