Add multi-buildpack to the top of buildpacks list

Signed-off-by: Thiago Belem <contato@thiagobelem.net>
Merge pull request #9 from TiuTalk/add-multi-buildpack

Add multi-buildpack to the top of buildpacks list
replacing gzip with pigz to improve slugbuild time

pigz is a parallel implementation of gzip that takes advantage of multiple cpus and has reportedly improved slug building results as seen here:
http://www.paasmag.com/2014/02/11/git-push-heroku-master-now-40-faster/

Signed-off-by: Paulo Fagiani <pfagiani@gmail.com>
Merge pull request #10 from fagiani/pigz

replacing gzip with pigz to improve slugbuild time
Merge remote-tracking branch 'upstream/master'