Add app.rb from branch 'solution'
Add app.rb from branch 'solution'

This file has been cleaned from its original implementation in the
'solution' branch to remove the solution to the exercise dealing with
the session.

Comments are added in spots where additional code must be filled in.

teddywing/Ruby-Web-Sessions-Exercise,teddywing/Ruby-Web-Sessions-Exercise,teddywing/Ruby-Web-Sessions-Exercise