Add picocsv benchmark

[charphi]

I've added a picocsv benchmark.

I've got some strange results: it seems that the performance greatly varies on the internal buffer size.
The default buffer size (8192) is less performant than a small buffer size.
On the other side, any multiple of the benchmark data size (163) is very performant.

Here are the numbers on my computer:

fastcsv:        4950990,093
picocsv 150:    4518949,433
picocsv 163:    7279028,970
picocsv 200:    4699804,914
picocsv 256:    4906056,524
picocsv 163*2:  7324703,236
picocsv 512:    4344949,147
picocsv 163*50: 7173802,419
picocsv 8192:   3520978,275

[osiegmar]

Thanks for your contribution!

For the sake of comparison, tweaking buffer sizes would only make sense if this is done for all contenders.

Speaking of comparison, I've updated https://github.com/osiegmar/JavaCsvComparison yesterday. You may want to check the settings of picocsv as I'm unsure if there are settings which would further improve the passed checks.

[charphi]

For the buffer size, you are right. That's why I let the default size in the benchmark.