jt/refactor config: update chefspec

Update ChefSpec to v3.2.0. This requires some spec changes, and
berkshelf changes in the spec_helper. Namely, rename the classes for
ChefSpec, and use chefspec's berkshelf integration. The berkshelf
vendor cookbook path issue is resolved w/ the ChefSpec version update.
jt/refactor config: config and service recipes

This commit moves the configuration directory and template resources
to a separate config recipe (as it was prior to commit 9c6deece65). It
also moves the service resources to a separate recipe. These changes
allow consumers of the cookbook to be more selective about what they
use from it, or use the default to get the full bowl of awesome.

* Add libraries/helpers methods for platform specific config that use
  the `platform_specific_path`s.
* Move the services to a separate recipe w/ a platform family case
  statement.
* Service resources subscribe to the config file.
* Update the specs.
jt/refactor config: update readme, default recipe

* Update README for refactored changes.
* Clarify intent of raised error in default recipe, on unsupported
  platforms.
Merge pull request #13 from opscode-cookbooks/jtimberman/refactor-redux

Refactor configuration and service resources to separate recipes