Remove dependency on puppetdb-terminus if storeconfigs is not used

[kpaulisse]

Overview

This pull request updates the documentation for configuring the path to Puppet, including tips on the puppetdb-termini gem, and eliminating the dependency on that gem in the Puppet run if storeconfigs is not used. It also adds (hopefully) reasonable defaults for locating the Puppet binary.

Inspired by #6

[kpaulisse]

Hey @dalen could you take a look at this and confirm this is doing what I expect and not introducing any side effects?

Basically in lib/octocatalog-diff/catalog-util/builddir.rb I changed the temporary copy of routes.yaml in the compilation directory to have facts - terminus = puppetdb changed to facts - terminus = yaml (or facts - terminus = facter). Keep in mind that alog-diff pulls facts from PuppetDB and sticks them in a YAML file before puppet is ever invoked, so puppet itself is not ever hitting puppetdb unless it's doing storeconfigs as well.

[dalen]

This looks reasonable as far as I can tell.