Should we add ffi-rzmq to the rutime dependency?

[kojix2]

Reported by @kozo2

[kojix2]

If you have IRuby installed and do not have the ZeroMQ binding installed, your browser will be blank. The error message is printed to the terminal. This is not kind to beginners.

[kojix2]

The messages that appear when you install a gem can be improved.

iruby/iruby.gemspec

Lines 21 to 22 in 7ed6d07

	m = "Consider installing the optional dependencies to get additional functionality:\n"
	File.read('Gemfile').scan(/gem\s+'(.*?)'/) { m << " * #{$1}\n" }

[kojix2]

Done!
#261