update version.

README

 Please checkout one of the release versions:
    git branch -a
 gives you all the available branches. 
+
 The newest release version is obtained with
-   git checkout releases/2.4
+   git checkout releases/2.5
+
+In the subfolder scripts a build script building the dune-fem-howto with all
+necessary dune module dependencies is available.
+
 This version should also be compatible with the development versions of the
 core. If you encounter problems please report (with all required
-information, e.g., which version on which sytem you are using) to
+information, e.g., which version on which system you are using) to
   dune-fem@dune-project.org