update README with v0.8 and update demo scripts to match

multinode-demo/client.sh

@@ -18,10 +18,8 @@ usage() {
   exit 1
 }
 
-if [[ -z $1 ]]; then
-  mkdir -p config-client
-  [[ -r config-client/client-id.json ]] || $solana_keygen -o config-client/client-id.json
-  $solana_bench_tps --identity config-client/client-id.json --network 127.0.0.1:8001
+if [[ -z $1 ]]; then # default behavior
+  $solana_bench_tps --identity config-private/client-id.json --network 127.0.0.1:8001 --duration 90
 else
   $solana_bench_tps "$@"
 fi