Use non-minified versions of zepto and offline-js.

(I also added an uglify offlinejs entry, for creating our own minified
version of offline-js, though we could, instead, use the one from the
top of the offline js distribution. Not sure which approach is more
future-proof/uncluttered/confusing.)
Include zepto promises implementation in build:

  $.Deferred()
Merge pull request #9 from kenmanheimer/master

Include non-minified offline-js and zepto, and add in zepto promises