CocoaPods installation guide in README.

Fixes #60.
Merge pull request #77 from wlue/master

CocoaPods installation guide in README.
Fix for crash when having a library that looks like a NSURLConnectionDelegate, like PubNub (which does responds to the 2 selectors injectIntoAllNSURLConnectionDelegateClasses checks on, but does not on currentRequest method.
Don't crash when exchangeSubviewAtIndex:withSubviewAtIndex: is called with invalid indices.
Also guard against exchangeSubview indices being negative. 

The UIView method doesn't crash in this case either.
Merge pull request #80 from ryanolsonk/defensiveExchangeSubviews

Fix crash in swizzled exchangeSubviewAtIndex:withSubviewAtIndex:
Merge pull request #79 from peterwilli/master

Fix for crash when having a library that looks like a NSURLConnectionDelegate, like PubNub
Merge remote-tracking branch 'upstream/master'