sudo gem install cocoapods报如下错误：
ERROR: While executing gem ... (Errno::EPERM)
Operation not permitted - /usr/bin/xcodeproj
解决的办法是：sudo gem install -n /usr/local/bin cocoapods
gem影像改成：https://ruby.taobao.org/
gem sources -l 列出服务器地址
gem sources --remove 列出的服务器地址
gem sources -a https://ruby.taobao.org/
)
