Linux Smelter support nested .zip buildpacks

GitHub produces .zips that look like this.

Bump src/inigo, src/linux-smelter

Bump cloudfoundry-incubator/inigo:
  Onsi Fakhouri:
     fix stager spec: smelter output has changed slightly
     use new ginkgo synchronized suite setup; refactor suite setup
     bump godeps
  Alex Suraci:
     removed snapshot tests
Bump cloudfoundry-incubator/linux-smelter:
  Onsi Fakhouri:
     bump testing framework
     Recurse into buildpacks if necessary