Added resumptionToken argument to allow imports to continue a previous import.

[seanBlommaert]

Hi,

Thanks for your awesome work. While working on a very large import it seemed nice to be able to allow batches of records in stead of importing everything at once. The applications keeps tracks of the resumptionToken and stores it locally. When doing the next batch, we start at the last known resumptionToken.

For this to work I've added the resumptionToken as an argument for ListRecords and ListIdentifiers (and off course to the RecordIterator). I've also added public methods to fetch the resumptionToken and the current batch, since we need the batch to determine when we want to store the new resumptionToken.

Would you consider adding this?

By the way, I've used this library to create a migration provider for Drupal (https://www.drupal.org/project/migrate_oaipmh). The Drupal migrate module allows for batch imports, so that was the main reason to start this. But I think it would make sense in other cases as well.

[caseyamcl]

Hi There,

Sorry for the delay! I've been out and about doing other things.

If you're still interested in merging this pull request, would you mind writing some Unit Tests for the change? I think it would work quite well.

[seanBlommaert]

I've extended the existing tests to include the new parameter. Is this enough? There is no test for the recordIterator, but I guess this is a seperate issue.

[caseyamcl]

This looks good! Thanks for the dilligence. Will release a new version today.

[seanBlommaert]

No problem! Thnx for the merge :)