Apparently hex only includes some files by default but not others
rather than a sane default of anything except for VCS directories. So
now I also get to maintain a list of files in my .app.src.

Apparently rebar3 can't generate a sane version number from Git tags and
adds a bunch of BS build number and ref tags which hex.pm then rejects.
Given that I can't find any documentation on how that works and reading
code is an exercise in over engineered abstractionism I've succumbed to
the demoralizing conclusion that I'll just have to go back to the dark
ages and maintain my versions both in source and in version control.

Time for Jiffy to enter the world of Erlang package management.

Multiple error reports on this.

Fixes #6

Passes all eep0018 tests.