cocoapods提示they required a higher minimum deployment targe

[!] Unable to satisfy the following requirements:

- `RxAlamofire (~> 3.0.0)` required by `Podfile`

Specs satisfying the `RxAlamofire (~> 3.0.0)` dependency were found, but they required a higher minimum deployment target.

原因是要添加的类库已经有最新版本推出，而Podfile文件并没有更改其下载版本（Podfile文件过期），于是获取安装数据失败。

首先：pod update --verbose

不行的话：

删除本地缓存，重新setup

$rm -fr ~/.cocoapods/repos/master

$pod setup