Add prerequisites and structure

Add a section about the prerequisites needed for this tutorial and how the
tutorial and the repository is structured.

README.md

@@ -27,10 +27,35 @@ $ apt-get install -y python3 python3-numpy python3-scipy python3-matplotlib
 ```
 -->
 
-# Prerequisites
-
-
-
+# Prerequisites and Structure
+
+This tutorial assumes that you have a little experience in python, which
+includes variable assignment, function calling and function definition, if statements and
+for loops. The tutorial uses only the very basics, such as variable assignments
+and function calls, but it is certainly advisable to know about control
+structures.
+
+To catch up on these aspects, you can refer to the [python
+documentation](https://docs.python.org/3/tutorial/).
+
+The tutorial is structured into several examples, which might depend on each
+other. The examples show code snippets which you are supposed to copy to a text
+editor. The scripts can then be executed in a terminal. You are invited to use
+the interactive mode of python or ipython instead of copying the code to a text
+editor. Recently jupyter notebooks have been
+become very popular. I recommend you to try out these different platforms and
+choose the one most suited for you.
+
+This repository does not contain ready-made python example scripts or plots.The
+only resource with code is this README file. The idea behind this is, that there
+shouldn't be duplications of code snippets, which will be out-of-sync eventually.
+The repository is set up, such that
+each commit triggers continues integration tasks, which parses the examples from
+the README and executes them with the
+[doxec](https://srv.sauerburger.com/esel/doxec) package. This means, you can
+download [read-made scripts and
+plots](https://srv.sauerburger.com/esel/FP-python-examples/-/jobs/artifacts/master/download?job=doxec_test)
+ produced by the continues integration task.
 
 # 'Hello World' Example
 The first example is basically a 'Hello World' script, to check whether python