Feature: Add "limit" condition

[Nikodem Jaworski]

I'd like to limit my results. Implementation should be possible without breaking something, right?

See: http://rethinkdb.com/api/javascript/limit/

[Wolfram Hempel]

I agree, adding a limit condition would be simple and would speed queries up. Temporarily though, retrieving a longer list and just not subscribing to its records shouldn't come with too much of an overhead.

[Michael Clark]

Would probably be most useful paired with https://www.rethinkdb.com/api/javascript/order_by/, which might be a little more complicated to implement (more options).

[Michael Clark]

Fix in #47