http://blog.csdn.net/dark_gmn/article/details/49274993
ERROR: Could not find a valid gem 'cocoapods' (>= 0), here is why:
Unable to download data from http://ruby.taobao.org/ - bad response Not Found 404 (http://ruby.taobao.org/specs.4.8.gz)
解决办法:换源地址
gem sources --remove http://ruby.taobao.org/ //移除原文件地址
gem sources -a https://ruby.taobao.org/ //添加新文件地址
gem sources -l //查看源文件地址是否正确
sudo gem install cocoapods //更新