This commit changes the Ruby request handler to read client
authentication info from trapperkeeper-authorization when tk-authz is
enabled via the `use-legacy-auth-conf: false` setting.  Support for the
pre-existing method of getting this info - via X-Client headers or an
SSL certificate, depending upon how the `master.allow-header-cert-info`
setting is configured - is preserved in the case that no information can
be derived from tk-authz.  tk-authz is presumed to provide client
authentication info via an `authorization` map within the Ring request
map.

This commit contains some updates to the `configuration.markdown` and
`external_ssl_termination.markdown` docs.  The updates pertain to new /
deprecated settings in Puppet Server per the integration of support for
trapperkeeper-authorization.

… helpers

This commit updates Puppet Server's trapperkeeper-authorization
dependency to 0.1.4 and updates some code to use some Ring helpers for
extracting authenticated client info.

This commit addresses some feedback on the associated PR:

* Fixes a couple of typos
* Pulls a when conditional up from a child form into its parent doseq