Use a more general method of installing the base puppet repositories

Our version of the "install repositories" step treated all redhat variants as
EL, which was incorrect. The new code is adapted from puppet and should work
across versions.
(maint) Remove AOT
Merge pull request #41 from aperiodic/nc-155-credential-leak

(NC-155) Fix credential leak
(maint) Disable JAR repacking when building RPMs

This repacking causes issues with clojure code.
(NC-160) Allow partial configuration of db-spec.

The user can specify any subset of `subprotocol`, `dbname`, `user`, and
`password` in the database section of the configuration file, and the
rest will be filled in with default values (and `dbname` will be renamed
to `subname` for the spec).
(NC-160) Add simple example to README.

Walk the user through creating a class, creating a group that references
it, and observing the classification of a node into said group.