(maint) add add'l platforms for acceptance testing

Prior to this commit, we were testing Hiera with a handful of platforms
whose system Ruby was 1.8.7. This led to some acceptance tests failing
when testing against the 'master' branch of Puppet (aka Puppet 4.0).

This commit adds additional platforms, whose system Ruby is 1.9.3+.
Merge pull request #218 from rji/maint/stable/addl-acceptance-platforms

(maint) add add'l platforms for acceptance testing
Merge remote-tracking branch 'upstream/stable'

* upstream/stable:
  (maint) add add'l platforms for acceptance testing
(fixup) beaker configs should end in .cfg
Merge branch 'stable'
(maint) only install libjson-ruby for ruby 1.8.7

JSON is included in stdlib beginning with Ruby 1.9.2. Therefore,
for our testing, it isn't needed except on platforms whose system
Ruby is 1.8.7.
Merge pull request #220 from rji/maint/stable/exclude-json-ruby193

(maint) only install libjson-ruby for ruby 1.8.7
Merge remote-tracking branch 'upstream/stable'

* upstream/stable:
  (maint) only install libjson-ruby for ruby 1.8.7
(HI-303) Add deep_merge dependency

Deep_merge is an optional dependency of Hiera. Call it out here so it
will be used when available.
Merge pull request #217 from MikaelSmith/bug/master/CPR-129-add-deep_merge-dep

(HI-303) Add deep_merge dependency
(HI-304) Make order override work with interpolation

The existing implementation of hiera interpolation did not utilize the
order override parameter of lookup. If an interpolated variable was
expected to be looked up in the overridden datasource it would instead
only be looked up in the configured datasources.

This patch passes the order_override parameter down the call stack to
the hiera_interpolate method of the Hiera::Interpolate class. This
method then in turn passes the order_override parameter back into the
Hiera::Backend lookup method. Thereby allowing the overridden datasource to
be searched for lookup values.
Merge pull request #221 from ssgelm/fix/master/HI-304-order-override-interpolation

(HI-304) Make order override work with interpolation