Adding ZipArchive 1.1.0 spec

This version of ZipArchive library adds some new methods over the one in Google Code repository which also hasn't been touched in several years.

Among fixes:

* typos
* compiler warnings
* updated for latest version of Xcode
* podspec updated to support OSX and iOS builds
* improved functionality: listing zip file contents and providing progress updates while expanding zip files.

Passes the pod lint.

My first Cocoa Pods contribution.. How did I go?