Create README.md

Create a small README file, documenting the main ideas of the project and its main features.

README.md

@@ -0,0 +1,41 @@
+# Vertretungen
+
+An android app designed to display published substitutions at the [Burgau-Gymnasium Düren](https://www.burgaugymnasium.de).
+
+## Installation
+
+This application is available in the Google Play Store. You can download it by searching for "Vertretungen am Burgau" or by clicking [here](https://play.google.com/store/apps/details?id=de.nils_beyer.android.testapplication).
+
+Currently, the app requires Android 4.2 or higher.
+
+In order to access the substitution system, you have to be able to login to the substitution system. Use the credentials you also use for checking the substitution table on the website.
+
+## Features
+
+- Display substitutions ordered by classes
+- Mark classes/courses
+- Login to the student and/or the teachers substitution system
+- Offline approach: The downloaded information are stored locally. You can simple open the app without internet connection in order to see the substitutions.
+- Offers one Android widget.
+
+## Libraries
+
+This project uses external libraries, including:
+
+- [Jsoup](https://github.com/jhy/jsoup) by [Jonathan Hedley](https://jhy.io/)
+- [GSON](https://github.com/google/Gson) by Google
+- [Android support libraries](https://developer.android.com/topic/libraries/support-library/packages.html)
+
+## Screenshots
+
+Main screen: Display all available classes listed online.
+
+![Main screen](https://lh3.googleusercontent.com/8VflNgJbIcxeywsbhHRlPOqtDPTXp2w8e5er237_TK3xkqpKkNgE6b6Nnhch6ixPjTw=w1340-h978)
+
+Detail screen: Display substitutions for a selected class: 
+
+![Detail screen](https://lh3.googleusercontent.com/eHLcK4bhKJHoCf6cjX8cnN5C0rVUyj2BirUkcG3tsPE7GbaVp0X5VIFYJ4loAcEL6gLo=w1340-h978)
+
+Login screen: Login to the substitution system.
+
+![Login screen](https://lh3.googleusercontent.com/8pQ-9Ht_U3A5bOoG6gD5j6K-E1400q9wlPI2fHJpkR1y2G_DjsOwqU1d72RpLZC5qA=w1340-h978)