Copy Sparkle.framework in a more sensible way

[webcracy]

The contents of Sparkle.framework are currently copied multiple times as a work-around to Rubygems not handling symlinks.

This is problematic, of course, because it bloats the source and the application with unnecessary code, and makes the development process more prone to confusion and error.

Possible solutions:

• Use a git submodule for the Sparkle files
• Have the user create the symlinks as part of rake sparkle:setup, or create a new rake task like rake sparkle:install
• Outsource that problem to a CocoaPod :)

[webcracy]

The solution was to use a zipball as suggested in #9. The zipball could prolly be downloaded post-install, or something, instead of being attached to the repo, but this is good enough for now.

[JonasNielsen]

This is awesome. Thanks a bunch @webcracy!