#284-add library banner or image in README.md

First attempt.

Author: schmouk

README.md

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+<img src="lib-banner.jpg" alt="library banner">
+
 # PyRandLib  [![license](http://img.shields.io/github/license/schmouk/pyrandlib.svg?style=plastic&labelColor=blueviolet&color=lightblue)](https://github.com/schmouk/pyrandlib/license)  [![Latest release](http://img.shields.io/github/release/schmouk/pyrandlib.svg?style=plastic&labelColor=blueviolet&color=success)](https://github.com/schmouk/pyrandlib/releases)  [![code_coverage](https://img.shields.io/badge/code_coverage-100%25-success?style=plastic&labelColor=blueviolet)]()  [![tests](https://img.shields.io/badge/tests-passed-success?style=plastic&labelColor=blueviolet)]()
 Many best in class pseudo random generators grouped into one simple library.