Add missing `r` to start up commands

[nogates]

Description

It looks like the default command to start zeus does not work anymore with ruby 2.5.1.

After digging around and reading some comments (1, 2), I've noticed that the versions below 2.5.1 were accepting -rubygems as a parameter, but this does not work anymore with version 2.5.1 and above

quico: ~ » ruby -v
ruby 2.3.1p112 (2016-04-26) [x86_64-linux-gnu]
quico: ~ »  ruby -rubygems  -e 'puts 1+1'
2
quico: ~ » rbenv shell 2.5.1            
quico: ~ » ruby -v
ruby 2.5.1p57 (2018-03-29 revision 63029) [x86_64-linux]
quico: ~ » ruby -rubygems  -e 'puts 1+1'
Traceback (most recent call last):
        1: from /home/nogates/.rbenv/versions/2.5.1/lib/ruby/2.5.0/rubygems/core_ext/kernel_require.rb:59:in `require'
/home/nogates/.rbenv/versions/2.5.1/lib/ruby/2.5.0/rubygems/core_ext/kernel_require.rb:59:in `require': cannot load such file -- ubygems (LoadError)

After adding that missing r, I can start zeus normally without having to do a zeus init and customizing the start command. Also, this works as well for versions prior 2.5.1

[nogates]

I guess this is related: https://github.com/rubygems/rubygems/pull/2269

[simi]

I think this is actually related to https://github.com/ruby/ruby/commit/e5e1f904d584bb8afd6f97f868c1fe896a572356.

[hsbt]

If zeus only supports Ruby 2.0+, It's better to remove -rrubygems from them.

[dcmorse]

Please merge this!