Use rvm in cron

1. rvm list
1. find what looks like your gems set, e.g
1. ruby-1.9.3-p194
2. echo $rvm_path/bin, e.g.
1. /usr/lib/rvm/bin
3. tack on the output of #1 to the output of #2, e.g.
1. /usr/lib/rvm/bin/ruby-1.9.3-p194
4. your cron entry should be the result of #3 followed by your ruby script, e.g.
1. 0 0 * * * /usr/lib/rvm/bin/ruby-1.9.3-p194 /optt/mydir/myscript.rb