前提：
安装位置：/usr/local/bin
cocoapods安装：
sudo gem install -n /usr/local/bin cocoapods
cocoapods安装指定版本：
sudo gem install -n /usr/local/bin cocoapods -v 1.10.0
cocoapods移除：
sudo gem uninstall -n /usr/local/bin cocoapods cocoapods-core cocoapods-deintegrate cocoapods-downloader cocoapods-plugins cocoapods-search cocoapods-stats cocoapods-trunk cocoapods-try
查看pod
pod --version
查看gem
gem list
*** LOCAL GEMS ***
activesupport (5.2.6)
addressable (2.7.0)
algoliasearch (1.27.5)
atomos (0.1.3)
bigdecimal (default: 1.4.1)
bundler (default: 1.17.2)
CFPropertyList (2.3.6)
claide (1.0.3)
cmath (default: 1.0.0)
cocoapods (1.10.0)
cocoapods-core (1.10.0)
cocoapods-deintegrate (1.0.4)
cocoapods-downloader (1.4.0)
cocoapods-plugins (1.0.0)
cocoapods-search (1.0.0)
cocoapods-trunk (1.5.0)
cocoapods-try (1.2.0)
colored2 (3.1.2)