[cleanup][script] change dune-version in install script to 2.8 and

update cmake version requirement in readme to match dumux

scripts/README.md

@@ -9,7 +9,7 @@ Installation guide dumux
 You can set up dumux using the attached script install.sh.
 You need to have the following REQUIREMENTS installed:
   * gcc >= 7
-  * cmake >= 3.1
+  * cmake >= 3.13
   * git
   * pkg-config
   * paraview (to visualize the results)

scripts/install.sh

@@ -75,7 +75,7 @@ echo " "
 echo "*********************************************************************************************"
 echo "(2/4) Cloning repositories. This may take a while. Make sure to be connected to the internet."
 echo "*********************************************************************************************"
-DUNE_VERSION=2.7
+DUNE_VERSION=2.8
 # the core modules
 for MOD in common geometry grid localfunctions istl; do
     if [ ! -d "dune-$MOD" ]; then