specified a static heroku-buildpack-nodejs version. fixes issue #181

[jpvillaseca]

Since the latest version of heroku-buildpack-nodejs is not the master branch, they recommend referencing specific versions by using tags, since master could (and is) unstable.

At the moment, heroku-buildpack-nodejs doesn't have a "latest" tag of sorts, so we have to put the latest version tag manually.

It fixes issue #181 related to dokku deployments failing due to that buildpack.

[edmorley]

Hi! I don't think pinning the Node.js buildpack is the best choice here.
The Dokku base image should be updated to include jq instead, for parity with the Heroku stack images.
(And in fact, I'm pretty sure the latest Herokuish images are based on the Heroku stack images, so perhaps you just need a docker pull?)

[mladenoff]

@jpvillaseca fwiw Heroku has added a latest tag