add map{3..6} instances to Nondeterminism, which can run 3-6 tasks in parallel and run the results through a function
rename map3, map4 etc to nmap3, nmap4 upon @paulchiasano's suggestion
Merge pull request #697 from stew/scalaz-seven

add nmap{3..6} instances to Nondeterminism, which can run 3-6 tasks in pa...