new port: devel/rubygem-ruby-progressbar

Ruby/ProgressBar is an extremely flexible text progress bar library for Ruby.
The output can be customized with a flexible formatting system including
percentage, bars of various formats, elapsed time and estimated time remaining.

WWW: https://github.com/jfelchner/ruby-progressbar

As this gem is based on the code that's available as misc/ruby-progressbar,
conflict with it, to avoid problems.