[doc] Intro

README.md

 # Getting and building this tutorial
 
-This document is work-in-progress. You should have a look at the
-excellent [getting started with Dune](http://www.math.tu-dresden.de/~osander/research/sander-getting-started-with-dune.pdf)
+This document gives a quick introduction in how to
+get and build Dune. Be warned that this document is work in progress.
+If you find an error feel free to open a corresponding issue.
+You may also want to have a look at the excellent
+[getting started with Dune](http://www.math.tu-dresden.de/~osander/research/sander-getting-started-with-dune.pdf)
 text by written by Oliver Sander.
 
 ## Prerequisites