Rubocop Sample config file and exempted cops in existing code

Take one or take both commits, but something to look at.

I will write something later in the README file to give hints on using Rubocop with exercise submissions.

re: #64 
Now that it is in, given time, we will likely get feedback on the
general feel for this as it applies here.  A simple change at that time,
if/when it is required.