#2431 Update version number in README.txt for upcoming release.

git-svn-id: https://chaste.cs.ox.ac.uk/svn/chaste/trunk@21846 b5f69653-2bf5-0310-8201-b0dafb8e1405
#2431 Might as well use the new scons style too.

git-svn-id: https://chaste.cs.ox.ac.uk/svn/chaste/trunk@21847 b5f69653-2bf5-0310-8201-b0dafb8e1405