nvm install v0.12.0 安装时报权限不足，
mkdir: cannot create directory ‘/home/ubuntu/.nvm/bin’: Permission denied
grep: /home/ubuntu/.nvm/bin/node-v0.12.0-linux-x64/node-v0.12.0-linux-x64.tar.gz: No such file or directory
Binary download failed, trying source.
mkdir: cannot create directory ‘/home/ubuntu/.nvm/src’: Permission denied
nvm: install v0.12.0 failed!
但是前面加了sudo 会直接报 sudo: nvm: command not found
sudo: nvm: command not found
