Slow reading of gzipped files

Following https://voxeu.org/article/which-programming-language-best-economic-research

The slow thing is:
```
 GZip.open("crsp_daily.gz","r") do io
    CSV.read(io, DataFrame)
end
```

@quinnj - do you think it is GZip.jl related or rather how CSV.jl and GZip.jl interact? 