add get version

tests/get_version.py

@@ -0,0 +1,9 @@
+#!/usr/bin/env python
+from panda import Panda
+
+if __name__ == "__main__":
+  for p in Panda.list():
+    pp = Panda(p)
+    print("%s: %s" % (pp.get_serial()[0], pp.get_version()))
+
+