pod install 报出下面的错误：
[!] Your Podfile requires that the plugin `cocoapods-acknowledgements` be installed. Please install it and try installation again.
解决方案：
gem install cocoapods-acknowledgements
有可能有权限问题可以使用一下命令：
sudo gem install cocoapods-acknowledgements
在执行:
pod install
要出现：
[!] Unable to satisfy the following requirements
使用
pod repo update
更新
