removed gc call for perf reasons.
Merge branch 'master' into dev

binging some bugfixes and two small features backtracks  into dev
Merge branch 'master' into dev
post release 2.2.0
better default for keyval
force keyval as reduce retval
improved adaptive read size algorithm
avoid sapply for data frames and matrices
debugging leftovers
Merge branch 'master' into dev
Merge branch 'master' into dev
next presentation in the making
readme for docs page
complete draft OCHUG presentation
version bump (working towards)
avro IO example
added live demo final command
hashing speedup
more scalable using distinct keys, one per map call
pass other args
get set number of records

we are not talking groups here