Performance improvement for CSV-lite and DKVP

[johnkerl]

DKVP before:

TIME IN SECONDS 8.439 -- tmlr cat /Users/kerl/tmp/big.dkvp
c58c621055443f591f1ea914c3c5421f  -

DKVP after:

$ justtime mlr cat ~/tmp/big.dkvp | md5sum
TIME IN SECONDS 4.487 -- mlr cat /Users/kerl/tmp/big.dkvp
c58c621055443f591f1ea914c3c5421f  -

CSV-lite before:

$ justtime mlr --csvlite cat ~/tmp/big.csv | md5sum
TIME IN SECONDS 5.661 -- tmlr --csvlite cat /Users/kerl/tmp/big.csv
8b9a5667759672170169a199653153b8  -

CSV-lite after:

$ justtime mlr --csvlite cat ~/tmp/big.csv | md5sum
TIME IN SECONDS 4.399 -- mlr --csvlite cat /Users/kerl/tmp/big.csv
8b9a5667759672170169a199653153b8  -