* Dscl user provider changes to support Mac 10.7, 10.8 & 10.9.
* Make the dscl user provider password handling idempotent.
* Refactor / modernize dscl user provider unit tests.
* Functional tests for dscl user provider.
Updates based on PR comments.
Changelog information for user dscl provider updates.
Merge pull request #1800 from opscode/sersut/chef#1634

DSCL User Provider Rewrite