Enable try-with-resources for RecordReader

org.apache.hadoop.mapred.RecordReader has a close method; but doesn't implement closeable; it would be nice to add that - it would enable to use:

try( org.apache.hadoop.mapred.RecordReader<?, ?> recordReader = inputFormat.getRecordReader(... )   ){
 [...]
}

...supporting t-w-r makes it easier to throw exceptions more safely