Add migration instructions to readme

Update list-all with 2.3.0 Ruby version. Thank you @Molly101 ~!

Ruby 2.3.0 is out!

https://www.ruby-lang.org/en/downloads/

Use GNU Readline if it's available. Thank you @andrewbredow ~!

A couple of popular Gems (Pry, Guard) do not function properly without
using GNU readline (e.g. [this GitHub
Issue](https://github.com/guard/guard/wiki/Add-Readline-support-to-Ruby-on-Mac-OS-X)).

This commit checks to see if GNU Readline has been installed via
homebrew on the Mac OS X and adds the proper `configure` argument. I
don't *think* this is an issue on Linux because GNU Readline seems to be
the default there.

Replace underscores with dashes in the get legacy version script filename

Add the first version of the get_version_from_legacy_file bash script.

Add ruby 2.2.2. Thank you @stevenschobert ~!