instance_variable_names remains for internal use, but it's not that useful for the users anymore

* I don't think people are running Rails under mongrel today
* it's better not to sudo gem install
* basically all we need to do is just bundle the server. No need to give its name as a parameter
* I could write ^^^, but I realized that it's not really about "command line"

This reverts commit 1a59a6df.

I guess it's not a typo: https://github.com/jorlhuda/exceptron

particularly, `all(options)` would warn