(HI-179) Add ability to log spec test order to a file

This commit is a copy of the implementation from
db0b27b52f60bf8cd2e7678009bbd00467b5f5ba of puppet, and I've included that
commit message below.

This commit tweaks the spec_helper to give it the
ability to log the spec test order to a file.  It
will only log the order if you have set the
environment variable "LOG_SPEC_ORDER", e.g.:

LOG_SPEC_ORDER=true rspec spec

This will be useful when using Nick L.'s bisect
script to identify order-dependent spec failures.
It should probably be enabled on all of our
Jenkins jobs, and would potentially allow us to
start running them with the random order flag
enabled.
(HI-179) Provide JUnit output for jenkins

This commit copies tasks/ci.rake and the ci:spec task from puppet
(5b723279b3ff14b1d411688f08608e669447c607). It also updates the Gemfile to
include the yarjuf gem in the developer/test sections.

Without JUnit style output we don't have a good way of seeing test
failures within jenkins. This adds a new rake task ci:spec that will
run with junit output, descriptive output and spec order logging.
Merge pull request #177 from haus/maint/stable/spec_and_bundler_fixins

(HI-179) Test Hiera against Ruby 2