added instructions for generating boot files

chapter_10/README

@@ -3,6 +3,10 @@ To build this code, run the following commands:
 erlc -o ./simple_cache/ebin ./simple_cache/src/*.erl
 erlc -o ./resource_discovery/ebin ./resource_discovery/src/*.erl
 
+Then run the following (all on a single line) to generate the .boot file:
+
+erl -pa ./simple_cache/ebin -pa ./resource_discovery/ebin -eval 'systools:make_script("simple_cache", [local])' -s init stop
+
 First start one or two contact nodes. Ensure that the node names
 in the sys.config files match your host name, and/or use -sname
 instead of -name. For example, do: