Install Pod error

Help got this error when installing pod

```
[!] /bin/bash -c
set -e
pushd CBitcoin
rm -rf Frameworks/
unzip -o -q Frameworks.zip
popd

~/Library/Caches/CocoaPods/Pods/Release/CBitcoin/0.2.2-8c3a2/CBitcoin ~/Library/Caches/CocoaPods/Pods/Release/CBitcoin/0.2.2-8c3a2
[Frameworks.zip]
End-of-central-directory signature not found. Either this file is not
a zipfile, or it constitutes one disk of a multi-part archive. In the
latter case the central directory and zipfile comment will be found on
the last disk(s) of this archive.
unzip: cannot find zipfile directory in one of Frameworks.zip or
Frameworks.zip.zip, and cannot find Frameworks.zip.ZIP, period.
```

首先重现 CocoaPods 安装失败，并检查错误中引用的 CBitcoin/Frameworks.zip 构件。确认该归档是否可以成功获取并解压，然后验证 pod 安装是否能够在没有所报告的 unzip 错误的情况下完成。

由索引模型根据 Issue 内容生成。