Release for CocoaPods

Made pod spec and other modifications to try and get functional with CocoaPods.

This created a problem where the .podspec file would not pass lint because of - WARN | [iOS] DSSparseArray/DSSparseArray/DSSparseArray.m:709:128: warning: values of type 'NSInteger' should not be used as format arguments; add an explicit cast to 'long' instead [-Wformat] warnings. I explicitly cast all the arguments so do not know where the problem was coming from. Ultimately I modified the .podspec file to specify the :osc platform to get around the problem even though the files are compatible with either iOS or OS X.

Fully functional sparse array implementation for objective c

This implementation should fully implement a sparse array functionality including, I am told, a working podspec (many thanks to Oggerschummer).

Almost complete functional version

A few more things could be added but nothing that cannot be easily worked around.