Resolve go.uuid breaking API changes

[bmaupin]

go.uuid has recently introduced breaking changes in their API:

$ go get github.com/bmaupin/go-epub
# github.com/bmaupin/go-epub
../../../go/src/github.com/bmaupin/go-epub/epub.go:134:44: multiple-value uuid.NewV4() in single-value context

Possible solutions:

• Lock dependencies to a specific tag/commit of go.uuid (e.g. 0633591)
  • I believe this will require checking in the vendor folder so that it will still work for users who are using go get instead of golang/dep
• Update to the new go.uuid API (missdeer/go-epub@ed07f4e)
  • There's lots of pushback regarding the new changes, probably best to wait
• Switch to another UUID library (e.g. google/uuid)
  • google/uuid might be a more official UUID library (breaking changes handled better), but doesn't yet have a stable API