当用homebrew安装node的时候，可能会报权限错误：
Error: The following directories are not writable by your user:
...
You should change the ownership of these directories to your user.
sudo chown -R $(whoami) /usr/local/share/man/man8解决办法，需要收回权限：
sudo chown -R `whoami`:admin /usr/local/bin
sudo chown -R `whoami`:admin /usr/local/share