Use Pathnames and singleton for cookbook_paths

Make it possible to manipulate the list when using Librarian or Berkshelf.
Add a method to add cookbook paths
Add Librarian's install directory to cookbook_paths
Split cookbook path array construction to helpers
Add unit tests for config path helpers
Add unit test that Librarian path is added to cookbook_paths
Use single line block for constructing expanded config paths
Merge pull request #226 from tmatilai/auto-add-librarian-dir

Automatically add Librarian's install directory to cookbook_paths
Remove extra spaces
Update changelog to reflect #226
Tweak changelog
Bump version after prerelease
install cookbooks from Berksfile if present

init generator will generate berkshelf files
Unify Librarian and Berkshelf methods and tests for Cook

- Remove hard dependency on Berkshelf gem
- Add `--no-berkshelf` option to disable cookbook installation
Unify Librarian and Berkshelf methods for Init
Add expand_path helper

Ensure that add_cookbook_path parameter is Pathname and expanded.
Allow Berkshelf path to be configured

Default to temporary directory.

TODO:

  - Tests
  - Remove tmpdir after syncing
  - Documentation
Include `:berkshelf` option to SoloBootstrap
Add a unit test for `solo clean`
Add Fedora 18 to known platform.