simplify readme

`plotfx` is a standalone tool for creating charts and other data-driven graphics.

It allows you to create and customize visualizations using a lightweight syntax

that is very similar to CSS. You can run PlotFX from the command line, where it

generates SVG, PNG and PDF output files. Additionally, you can embed it into your

own application using the C API.

Charts can be customized using a lightweight syntax that is very similar to CSS.

You can run PlotFX from the command line, where it generates SVG, PNG and PDF

output files. Additionally, you can embed it into your own application using the

C API.

PlotFX is partially based on ideas from the "Grammar of Graphics" [0].

One of the main goals for PlotFX is that using it should be simple and fun.

One of the main goals for PlotFX is that creating charts should be quick, simple

and fun.

**WARNING**: The project is currently a work-in-progress. I'm currently working

on removing the old SQL chart specification language and replacing it with the

Here is how to create a simple line chart using plotfx:

    $ plotfx -in example_chart.plot -out example_chart.svg

    $ plotfx -in example_chart.ptx -out example_chart.svg

Output File (`example_chart.svg`):

[![A simple line chart](./examples/linecharts/lines_with_points.svg)](./examples/linecharts/lines_with_points.plot)

[![A simple line chart](./examples/linecharts/lines_with_points.svg)](./examples/linecharts/lines_with_points.ptx)

Input File (`example_chart.plot`):

Input File (`example_chart.ptx`):

    width: 1200px;

    height: 480px;