ignore Bundler binstub-generated directories

I run my `bundle install` commands with the `--binstubs` option so no 
`bundle exec` is required.  This commit ensures the generated 
directories are properly git ignored in generated cookbooks.
Merge pull request #309 from schisamo/gitignore-bundler-binstubs

Ignore Bundler binstub-generated directories
If a relative :path is in Berksfile, keep it relative in Berksfile.lock.

It's inconvenient to have absolute paths in Berksfile.lock 
when it is under version control and shared.
Merge pull request #310 from rectalogic/relative-path

If a relative :path is in Berksfile, keep it relative in Berksfile.lock.
style refactors from previous commit
Convert UI to module
Monkey patch Thor Shell instead
Don't autoload UI, since it's not used by Berkshelf directly anymore
Name UI in set_ui
Remove dangling require clause
Read maintainer info from Berkshelf::Config
Fix failing spec
Also check Chef::Config
Make Berkshelf threadsafe (again)
Add specs
Merge pull request #316 from sethvargo/threadsafe

Make Berkshelf threadsafe (again)
Enable Guard notifications
Fix failing specs (I think)
Merge pull request #317 from RiotGames/enable-guard-notification

Enable Guard notifications
Merge pull request #314 from sethvargo/vagrant_ui

Convert UI to Module