CocoaPods版本升级

当你遇到下面的场景时就表示需要升级Cocoapods了
the version of cocoapods used to generate the lockfile (1.9.1) is higher than the version of ...

1. 可以查看下自己的cocoapods版本号
   执行命令：pod --version
   结果：1.8.4

2. 查看cocoapods源
   执行命令：gem sources -l
   结果:

*** CURRENT SOURCES ***

https://gems.ruby-china.com

3. 安装或者更新cocoapods
   执行命令：sudo gem install cocoapods
   接着输入电脑登录密码
   结果：

Fetching ffi-1.12.2.gem
Fetching ethon-0.12.0.gem
Fetching cocoapods-core-1.9.1.gem
Fetching xcodeproj-1.15.0.gem
Fetching cocoapods-1.9.1.gem
Fetching typhoeus-1.3.1.gem
Building native extensions. This could take a while...
Successfully installed ffi-1.12.2
Successfully installed ethon-0.12.0
Successfully installed typhoeus-1.3.1
Successfully installed cocoapods-core-1.9.1
Successfully installed xcodeproj-1.15.0
Successfully installed cocoapods-1.9.1
Parsing documentation for ffi-1.12.2
Installing ri documentation for ffi-1.12.2
Parsing documentation for ethon-0.12.0
Installing ri documentation for ethon-0.12.0
Parsing documentation for typhoeus-1.3.1
Installing ri documentation for typhoeus-1.3.1
Parsing documentation for cocoapods-core-1.9.1
Installing ri documentation for cocoapods-core-1.9.1
Parsing documentation for xcodeproj-1.15.0
Installing ri documentation for xcodeproj-1.15.0
Parsing documentation for cocoapods-1.9.1
Installing ri documentation for cocoapods-1.9.1
Done installing documentation for ffi, ethon, typhoeus, cocoapods-core, xcodeproj, cocoapods after 33 seconds
6 gems installed

4. 更新完之后，查看下pod版本号
   执行命令：pod --version
   结果：1.9.1

到此，cocoapods升级完成了。