Lock Berkshelf to v3.1.5
Only run unit tests in ChefDK verify

The Berkshelf cucumber tests are failing because they make assumptions 
about latest versions of cookbooks on Supermarket. The `berkshelf-api` 
cookbook received an update today that broke the tests!
Merge pull request #242 from opscode/schisamo/lock-berks-down

Lock Berkshelf Down; Only run ChefDK unit tests
Updated Omnibus with `appbundle` DSL
Use Omnibus’s new `appbundle` method in Builder DSL
Perform `rubygems-customization` after all gems are installed

This ensures bundle installs that are executed during the Omnibus build
don’t end up in the build user’s home directory:

  `~/.chefdk/gem/ruby/2.1.0/gems/`
Bin files from non-Appbundled gems belong in `embedded/bin`
Remove crazy PATH on Chef Windows gem `bundle install`

`with_embedded_path` does the right thing now.
No need to delete the Windows gem on Chef install

Since we create the gems with targeted `gem build` commands there is
nothing to delete any longer!
Merge pull request #243 from opscode/schisamo/appbundle-dsl

Leverage `appbundle` DSL
Update to omnibus cookbook 2.3.4

This version contains some fixes/improvements for Windows environments.
Add instructions for using Windows in TK build lab

/cc @adamedx @jdmundrawala @btm
Updated `omnibus-software` w/ dep-selector-libgecode fix

Changes detailed here: opscode/omnibus-software/#298
Updated `omnibus` with leaky Ruby ENV fix
Enable feature migration for chef-windows msi