Add some tests that verify (a) vimap is properly streaming, respecting both the max_total_in_flight parameter, and producing output before grabbing futher input from an input generator (b) a big fork operation scatters work to worker processes correctly.
Changes from Boris' code review, thanks!
Merge branch 'master' into gatoatigrado-streaming-and-big-fork-test
Add clarifying comment
Merge pull request #11 from gatoatigrado/gatoatigrado-streaming-and-big-fork-test

Add some tests ... [sheep'd by zabra]