Merge branch 'cleanup/installscript_to3.0' into 'master'

[script] checkout the correct release

See merge request !56

scripts/install.sh

@@ -85,12 +85,12 @@ cd ..
 
 # dumux
 if [ ! -d "dumux" ]; then
-    git clone -b master https://git.iws.uni-stuttgart.de/dumux-repositories/dumux.git
+    git clone -b releases/3.0 https://git.iws.uni-stuttgart.de/dumux-repositories/dumux.git
 else
     echo "Skip cloning dumux because the folder already exists."
 fi
 cd dumux
-git checkout dumux-course-2018
+git checkout releases/3.0
 cd ..
 
 # dumux-course