Improve README

git-svn-id: file:///git/lcgcool.svndb/cool/trunk@20259 4525493e-7705-40b1-a816-d608a930855b

src/PyCool/tests/root8458/README

 ssh lxplus6
 cd /tmp/$USER
+rm -rf /tmp/$USER/root8458
 svn co svn+ssh://svn.cern.ch/reps/lcgcool/cool/trunk/src/PyCool/tests/root8458
 
 cd /tmp/$USER/root8458