MKStoreKit includes NSData+Base64.m which causes conflicts with other pods

[paulw11]

MKStoreKit includes NSData+Base64.m and NSData+Base64.h in its source. This causes duplicate symbol conflicts if you use another Pod that includes a dependency on the NSData+Base64 pod

Either modify these files so that they use a prefixed set of symbols and avoid the clash or preferably declare NSData+Base64 as a dependency for this Pod