add CHANGELOG, AUTHORS files

Here is an inevitably incomplete list of contributers who have submitted

patches, reported bugs, added translations, helped answer newbie questions, and

generally made PlotFX better (ordered by time of first contribution)

- Paul Asmuth <paul@asmuth.com>

- Laura Schlimmer <lauraschlimmer@gmail.com>

PlotFX v0.2.0; unreleased

  * Renamed the project from "FnordMetric" to "PlotFX", set version to "0.2.0"

  * Changed the license to 3-Clause BSD

  * Removed the old ChartSQL SQL engine

  * Added a new configuration frontend with a CSS-like syntax

  * Added support for reading input data from CSV files

  * Added support for embedding PlotFX as a library

  * Added support for exporting images as bitmaps (PNG) and PDF files through

    libcairo

  * Added support for non-latin text shaping through libharfbuzz

  * Ported the existing elements from the old codebase (see git): areas, axis,

    bars, gridlines, legend, lines, points

  * Added the new 'box' element and a simple box layout model