gem list cocoapods
*** LOCAL GEMS ***
cocoapods (1.8.4, 1.5.3, 1.4.0.beta.1)
cocoapods-core (1.8.4, 1.5.3, 1.4.0.beta.1)
cocoapods-deintegrate (1.0.4, 1.0.2, 1.0.1)
cocoapods-downloader (1.2.2, 1.2.0, 1.1.3)
cocoapods-plugins (1.0.0)
cocoapods-search (1.0.0)
cocoapods-stats (1.1.0, 1.0.0)
cocoapods-trunk (1.4.1, 1.3.1, 1.3.0)
cocoapods-try (1.1.0)
sudo gem uninstall cocoapods -v 1.5.0 //這個是用用來刪除cocoapods的
sudo gem uninstall cocoapods-core -v 1.5.0 //這個是用來刪除cocoapods-core的