Updating berkshelf Gem

There was a cascade of updates required to be compatible with a major
version bump in the hashie gem.

Here's the error that I'm fixing:

```
~/src/chef-postgis (master) ✗ kitchen list
!!!!!! The `berkshelf' gem is missing and must be installed or cannot be properly activated. Run `gem install berkshelf` or add the fol
lowing to your Gemfile if you are using Bundler: `gem 'berkshelf'`.
>>>>>> ------Exception-------
>>>>>> Class: Kitchen::UserError
>>>>>> Message: Could not load or activate Berkshelf (cannot load such file -- hashie/hash_extensions)
```