Update library-using.md
At Donn's suggestion, added 3rd env var option, at bottom of doc:
"...
or:
`SCOPE_CRIBL=tcp://host:port`
"
@@ -95,3 +95,5 @@ You must also tell AppScope where to deliver events. This can be accomplished by
- `SCOPE_CONF_PATH=lib/scope.yml`
or:
- `SCOPE_EVENT_DEST=tcp://localhost:9999`
+or:
+- `SCOPE_CRIBL=tcp://host:port`
