我按照在Mac上安装Polymer 3.0的步骤进行操作，最后一步出现此错误：
Edgars-MacBook-Pro:~ edgar$ sudo npm install -g polymer-cli
Password:
/Users/edgar/.npm-global/bin/polymer -> /Users/edgar/.npm-global/lib/node_modules/polymer-cli/bin/polymer.js
+ polymer-cli@1.8.1
added 12 packages, removed 6 packages and updated 7 packages in 4.804s
Edgars-MacBook-Pro:~ edgar$ polymer --version
-bash: polymer: command not found