Bugfix: handle more than one document

Hello there!
First, thanks for this library. It makes my life easier.
I've noticed that Mendeley, when asked for '-1' documents, doesn't return the full list of documents in the library anymore (as they have implemented paging).
I'm attaching a super-quick fix, that downloads 1k documents at once, although the correct fix should be to handle paging, so that people trying out your awesome code can see it working.

Ciao!