[trac614] Update readme

tools/README

@@ -1,3 +1,4 @@
 The "tools" directory contains scripts for helping the BIND 10
-developers maintain the source tree. These are not intended
-to be built nor installed by the build system.
+developers with various tasks, eg. maintaining the source tree,
+running some tests. These are not intended to be built nor
+installed by the build system.