WISH: Update binReadCounts() to read in chunks by default

[HenrikBengtsson]

Maybe we should update binReadCounts() to read in chunks by default. This should lower the risk for users running into hard-to-troubleshoot memory issues, e.g. #100.

Suggestion

• Set a default value for argument chunkSize, e.g. chunkSize = 10e6
• Until future.apply 1.9.0 is on CRAN, add a run-time check for future (>= 1.22.1)