Change LogReader API to be able to replace messages

The mutation API in LogReader was not able to express dropping messages,
or growing messages.  This enables more aggressive mutation.

Change-Id: I477482da4262483a780d15ebf8c98a51e37099f6
Signed-off-by: James Kuszmaul <james.kuszmaul@bluerivertech.com>
diff --git a/aos/flatbuffers/base.h b/aos/flatbuffers/base.h
index ff81c9a..a92cc91 100644
--- a/aos/flatbuffers/base.h
+++ b/aos/flatbuffers/base.h
@@ -1,5 +1,6 @@
 #ifndef AOS_FLATBUFFERS_BASE_H_
 #define AOS_FLATBUFFERS_BASE_H_
+
 #include <stdint.h>
 #include <sys/types.h>
 
@@ -15,6 +16,7 @@
 #include "glog/logging.h"
 
 namespace aos::fbs {
+
 using ::flatbuffers::soffset_t;
 using ::flatbuffers::uoffset_t;
 using ::flatbuffers::voffset_t;