RubyLearning Skeleton with empty course files.

This skeleton is arranged to make it simple to tab complete any exercise
or challenge that we need to get to.  The naming convention is of
course, the week number, the files are named with a number and a code to
express an exercise or a challenge, or perhaps an addendum.

The common letter codes after the number will be 'e' and 'c' for
exercise and challenge, respectively.