Create C++ -> Python interface for calling LogReader

This provides an interface that allows the user to extract json data
from the logfiles directly into Python.

Change-Id: Iafd1e4ac2301befe1f8939b396d6e40a3133b2a2
diff --git a/aos/events/logging/logger.cc b/aos/events/logging/logger.cc
index e35fe5b..1c2815d 100644
--- a/aos/events/logging/logger.cc
+++ b/aos/events/logging/logger.cc
@@ -269,6 +269,10 @@
   QueueMessages();
 }
 
+LogReader::~LogReader() {
+  CHECK(!event_loop_unique_ptr_) << "Did you remember to call Deregister?";
+}
+
 bool LogReader::ReadBlock() {
   if (end_of_file_) {
     return false;