Log Message:
Add ruby-powerbar 1.0.18 which is required by archivers/ruby-minitar-cli.

# PowerBar

This is PowerBar - The last progressbar-library you'll ever need.

## Features

* Detects when stdout is not a terminal and automatically falls back to logging
  * Does not clutter your log-files with ansi-codes!
  * If your CLI-app can run interactively and non-interactively (e.g. cronjob)
    you will automatically get reasonable progress-output in both modes.
  * By default prints to stderr but can call any output-method
    of your choice (e.g. your favorite Logger).

* Fully customizable; all output is template-driven.

* All output is optional. You may set PowerBar to silently collect progress
  information (percentage-done, throughput, ETA, etc.) and then use the
  computed values elsewhere in your app.

* All state can be updated at any time. For example: If you're monitoring a
  multi-part operation then you can change the status-message of a running
  PowerBar to reflect the current state.