`launchd` doesn't allow you to *use* environment variables. Nor does it support
tilde-expansion of program names & arguments after OSX 10.10.
To work around this, I've made the plist file a template and included a small
install script that will interpolate the correct values.
Does auto-complete for the ipfs commands, subcommands and parameters.
Reported to works for bash and zfs
The completion could be smarter for some parameters (marked as #TODO)
