message: External leveldb link changed
  table_format.txt was renamed to table_format.md
diff: @@ -5,4 +5,4 @@ The table format is similar to the table format for the LevelDB
  open source key/value store, with the exception that our tables
  do not support "filter" meta blocks (Bloom Filters). See:
  -https://github.com/google/leveldb/blob/master/doc/table_format.txt
  +https://github.com/google/leveldb/blob/master/doc/table_format.md
  