Respect custom output stream in csvstack.
Respect custom output stream in csvstack.

arowla/csvkit,archaeogeek/csvkit,Tabea-K/csvkit,KarrieK/csvkit,snuggles08/csvkit,Jobava/csvkit,wireservice/csvkit,matterker/csvkit,jpalvarezf/csvkit,cypreess/csvkit,kyeoh/csvkit,gepuro/csvkit,bradparks/csvkit__query_join_filter_CSV_cli,barentsen/csvkit,metasoarous/csvkit,dannguyen/csvkit,doganmeh/csvkit,unpingco/csvkit,aequitas/csvkit,wjr1985/csvkit,moradology/csvkit,tlevine/csvkit,nriyer/csvkit,themiurgo/csvkit,elcritch/csvkit,onyxfish/csvkit,haginara/csvkit,reubano/csvkit,bmispelon/csvkit