Update usage

msa_limit.py

@@ -58,6 +58,9 @@ def usage():
         "         -p <string> ",
         "            default: nothing",
         "            Prefix for results folders."
+        "         -d ",
+        "            default: false",
+        "            Show diploid metrics."
         "  run_config <string> <string> ...",
         "       Launches the pipeline from configuration file(s)",
         "        required: path to the configuration file(s).",