Exit as error on activation failures
Unset shell version only if the `deactivate` has invoked
Exit as error on deactivation failures
Add `--quiet` option to `activate` and `deactivate`
Fix fish syntax error at `else`
s/QUIET/NOERROR/g
Display information on automatic (de)?activation
Fix `virtualenv-prefix` when the version is `system`
Fix issues with manual activation of virtual environments (#34)