Use separate app and build directories to match Heroku.

Signed-off-by: Michael Elsdoerfer <michael@elsdoerfer.com>
Support buildpacks creating an empty release file.

Ruby 1.9's YAML cannot load empty files, thus we have to test earlier.

Signed-off-by: Michael Elsdoerfer <michael@elsdoerfer.com>
Merge pull request #6 from miracle2k/patch-1

Support certain (older?) buildpacks