Update README: document known discrepancies
Update README: document known discrepancies

matwey/rebar,norton/rebar3,paulo-ferraz-oliveira/rebar,evnix/rebar,macintux/rebar,apache/couchdb-rebar,blt/rebar3,paulo-ferraz-oliveira/rebar,evnix/rebar,csyangchen/rebar,scatterbrain/rebar,thomasbhatia/rebar,beni55/rebar-1,choptastic/rebar,fishcakez/rebar3,dcarastan/rebar,CMoH/rebar,surik/rebar3,bsmr-erlang/rebar,jacktang/rebar,heroku/rebar,fabiankrol/rebar3,GabrielNicolasAvellaneda/rebar,matwey/rebar,platinumthinker/rebar,benoitc/rebar3,choptastic/rebar,K2InformaticsGmbH/rebar,CMoH/rebar,norton/rebar,SiDen/rebar,lpgauth/rebar,syl20bnr/rebar,lrascao/rebar,choptastic/rebar,matwey/rebar,syl20bnr/rebar,basho/rebar,processone/rebar3,csyangchen/rebar,K2InformaticsGmbH/rebar,bsmr-erlang/rebar,SiDen/rebar,fauxsoup/rebar3,deadok22/rebar,fauxsoup/rebar3,norton/rebar,dcarastan/rebar,apache/couchdb-rebar,thomasbhatia/rebar,lrascao/rebar3,bsmr-erlang/rebar,scatterbrain/rebar,scatterbrain/rebar,sile/rebar3,blt/rebar3,rebar/rebar,apache/couchdb-rebar,heroku/rebar,linearregression/rebar3,rebar/rebar3,linearregression/rebar3,benoitc/rebar3,rebar/rebar,thomasbhatia/rebar,saleyn/rebar3,shkumagai/rebar,macintux/rebar,matwey/rebar,jacktang/rebar,project-fifo/rebar3,wcy123/rebar,jbalint/rebar3,platinumthinker/rebar,lrascao/rebar,K2InformaticsGmbH/rebar,walrusVision/rebar3,cloudant/couchdb-rebar,walrusVision/rebar3,zugolosian/rebar3,RubberCthulhu/rebar,beni55/rebar,djnym/rebar3,RubberCthulhu/rebar,surik/rebar3,sile/rebar3,CMoH/rebar,lrascao/rebar,GabrielNicolasAvellaneda/rebar,beni55/rebar-1,basho/rebar,dcarastan/rebar,beni55/rebar,lpgauth/rebar,oubiwann/rebar,oubiwann/rebar,evnix/rebar,platinumthinker/rebar,lrascao/rebar,GabrielNicolasAvellaneda/rebar,cloudant/couchdb-rebar,zugolosian/rebar3,jbalint/rebar3,macintux/rebar,K2InformaticsGmbH/rebar,oubiwann/rebar,shkumagai/rebar,matwey/rebar,K2InformaticsGmbH/rebar,tsloughter/rebar3,csyangchen/rebar,erlang/rebar3,norton/rebar,vladdu/rebar3,lrascao/rebar,SiDen/rebar,cloudant/couchdb-rebar,shkumagai/rebar,norton/rebar,fabiankrol/rebar3,kellymclaughlin/rebar3,syl20bnr/rebar,wcy123/rebar,rebar/rebar,deadok22/rebar,paulo-ferraz-oliveira/rebar,processone/rebar3,beni55/rebar,project-fifo/rebar3,lpgauth/rebar,jacktang/rebar,rebar/rebar3,ferd/rebar3,bsmr-erlang/rebar