Initial commit.
Configure the app through environment variables.

This is so we can put a demo on heroku.
Add Procfile as specified in the buildpack.

See heroku-buildpack-vibe.d for more information [1].

[1] - https://github.com/skirino/heroku-buildpack-vibe.d#required-settings-of-vibed-project
Add lflags field to the dub.json.

Like the previous commit, this is simply following instructions from the
buildpack.