feat: allow rows parameter and no pagination (get first n elements)

[manuelguzmandao]

There are 2 contributions in the PR:

1. Allow using the rows parameter in the request: sets the size of the page to retrieve. This allows to get the first n elements (used with the pagination off) and to retrieve bigger pages in case of harvesting to reduce the amount of requests to the API.
2. Turn pagination off: used with the rows parameter, it allows to get the first n elements of a request (the most pertinent ones).

Usage:

works = Works(request_params={'rows': 5}, pagination=False)
query = works.filter(<your filter>) # the first 5 elements will be retrieved
for item in query:
    do someting...

This PR handles issue #13