(maint) Fix useradd spec when using ruby-shadow 2.3.3.

The ruby-shadow gem inserted a new member into the PasswdEntry struct in 2.3.3.
This caused a useradd provider spec to fail that was relying on a member that came after the newly inserted member.
The failure only occurs when the ruby-shadow gem is installed.

The fix is to populate the struct members by name rather than relying on the member order.
(maint) Change Travis CI to output documentation format for specs.

We've been observing a sporadic "rake aborted" failure on Travis CI.
This change turns on "documentation" format for rspec so that we can
at least see if the test run is aborting on the same test each time.
Merge pull request #2406 from peterhuene/travis/documentation

(maint) Change Travis CI to output documentation format for specs.
Merge branch 'master' of https://github.com/puppetlabs/puppet