在用PKg安装cario的时候出现错误，julia error building homebrew.
解决办法，对julia包目录赋予写权限。
sudo chown -R $(whoami) /Users/grantbai/.julia
参考：https://github.com/JuliaPackaging/Homebrew.jl/issues/59
using Homebrew
Homebrew.rm("libpng")
Homebrew.add("libpng")
Pkg.build("Cairo")
using Homebrew
Homebrew.rm("libpng")
Homebrew.add("libpng")
Homebrew.rm("cairo")
Homebrew.add("cairo")
Homebrew.rm("pango")
Homebrew.add("pango")
Pkg.build("cairo")