Removed version definition for CocoaAsyncSocket

Robbie Hanson has updated the version number of CocoaAsyncSocket which makes it difficult to integrate this pod because of the version definition. I've removed the version requirement, it is compatible with the latest release.
Update CocoaHTTPServer.podspec
Merge pull request #2327 from Zyphrax/master

Removed version definition for CocoaAsyncSocket