Correctly handle subcommand help

etherdump --help and etherdump CMD --help should work.

bin/etherpump

@@ -52,16 +52,18 @@ try:
     else:
         args = sys.argv[2:]
 
-    if any(arg in args for arg in ['--help', '-h']):
+    if len(sys.argv) < 3:
-        print(usage)
+        if any(arg in args for arg in ['--help', '-h']):
-        sys.exit(0)
+            print(usage)
-    elif any(arg in args for arg in ['--version', '-v']):
+            sys.exit(0)
-        print('etherpump {}'.format(__VERSION__))
+        elif any(arg in args for arg in ['--version', '-v']):
-        sys.exit(0)
+            print('etherpump {}'.format(__VERSION__))
+            sys.exit(0)
 
 except IndexError:
     print(usage)
     sys.exit(0)
+
 try:
     # http://stackoverflow.com/questions/301134/dynamic-module-import-in-python
     cmdmod = __import__(