BLD: tox, don't clean up build dir, permissions often get in the way

Author: y-p

tox.ini

@@ -23,7 +23,7 @@ commands =
     # TODO:  --exe because of GH #761
     {envbindir}/nosetests --exe pandas.tests -A "not network"
     # cleanup the temp. build dir created by the tox build
-    /bin/rm -rf {toxinidir}/build
+#    /bin/rm -rf {toxinidir}/build
 
     # quietly rollback the install.
     # Note this line will only be reached if the

tox_prll.ini

@@ -24,7 +24,7 @@ commands =
     # TODO:  --exe because of GH #761
     {envbindir}/nosetests --exe pandas.tests -A "not network"
     # cleanup the temp. build dir created by the tox build
-    /bin/rm -rf {toxinidir}/build
+#    /bin/rm -rf {toxinidir}/build
 
     # quietly rollback the install.
     # Note this line will only be reached if the