Add RetryableRecordReader

[fmbenhassine]

as of version 4.x, it is possible to use a retry policy for the record reader ( #175 ). This feature is currently handled by the framework in the job implementation.

The idea is to provide a way to decorate all readers with a retry feature in a RetryableRecordReader :

RecordReader recordReader = new RetryableRecordReader(
   new UnreliableDataSourceReader(),
   new RetryPolicy(3, 500, TimeUnit.MILLISECONDS);
);

[fmbenhassine]

added in 5633e67