pass bin/release $build_root instead of $app_root

Needed by heroku-buildpack-ruby
Merge pull request #56 from icco/patch-1

pass bin/release $build_root instead of $app_root
comprehend buildpack urls with treeish components
Use https://github.com/CHH/heroku-buildpack-php as the builtin PHP buildpack
Merge pull request #57 from qrohlf/patch-1

Use https://github.com/CHH/heroku-buildpack-php as the builtin PHP buildpack
use the build root to build the release file
updating authors
Merge pull request #58 from nolman/fixing-ruby-heroku-buildpack

Fixing ruby heroku buildpack
Added libmcrypt-dev
Merge pull request #62 from jbrooksuk/patch-1

Added libmcrypt-dev
Use a subdirectory of /cache

Heroku tends to remove the /cache directory.
This causes issues with dokku, when we mount it using docker volumes.
So make the buildpacks use a subdirectory of the mount point.
Merge pull request #64 from plietar/cache-subdir

Use a subdirectory of /cache
Add support for jekyll
Merge pull request #65 from pandrew/30-jekyll-buildpack

Add support for jekyll
Group heroku's buildpacks together
Consistently add .git for git URLs
Add missing heroku's default buildpacks

Probably makes sense to have all of Heroku's [default
buildpacks](https://devcenter.heroku.com/articles/buildpacks#default-buildpacks)
available in Dokku.

Added:

- gradle
- grails
Merge pull request #67 from amaltson/missing-heroku-default-buildpacks

Add missing heroku's default buildpacks
Add instructions on how to create an application tar
Add heroku buildpack multi