Ensure appropriate minimum alignment on flatbuffer tables

If you had a table whose fields all had alignments of <4 bytes, the
overall table still needed to have 4 byte alignment to account for the
various offsets included in every table.

Change-Id: I7c39c647d79dff80732f84c4e530319ee8f20c99
Signed-off-by: James Kuszmaul <james.kuszmaul@bluerivertech.com>
diff --git a/aos/flatbuffers/test.fbs b/aos/flatbuffers/test.fbs
index 9369bd1..97b0fef 100644
--- a/aos/flatbuffers/test.fbs
+++ b/aos/flatbuffers/test.fbs
@@ -8,6 +8,10 @@
   y:double;
 }
 
+table MinimallyAlignedTable {
+  field:ubyte (id: 0);
+}
+
 table SubTable {
  foo:short (id: 0);
  bar:short (id: 1, deprecated);