ReactiveCocoa学习

http://www.jianshu.com/p/e10e5ca413b7
http://www.jianshu.com/p/87ef6720a096
http://blog.csdn.net/fly1183989782/article/details/62053973

Unknown warning group '-Wreceiver-is-weak', ignored

`pod ``'ReactiveCocoa'``, :git => ``'[https://github.com/zhao0/ReactiveCocoa.git](https://github.com/zhao0/ReactiveCocoa.git)'``, :tag => ``'2.5.2'`