chefdk-update-app to update Chef version in ChefDK

# Run help to see available commands, apps.
$ ./bin/chefdk-update-app.sh -h
Usage: ./bin/chefdk-update-app.rb APP_NAME [options]
    -r, --ref REF                    Git reference (branch, tag, sha, etc.)
    -h, --help                       Prints this help

App names:
    * berkshelf
    * chef
    * chef-dk
    * chef-vault
    * foodcritic
    * ohai
    * test-kitchen
    
# Update chef to 12.2.1
[21:21:49] (23) jreid@JoesMacBookPro:~/repo/chefdk-update-app(master)
$ sudo ./bin/chefdk-update-app.sh chef -r "12.2.1"
Password:
-----> Cleaning chef checkout
-----> Cloning chef from https://github.com/chef/chef.git
Cloning into '/opt/chefdk/embedded/apps/chef'...
remote: Counting objects: 115433, done.
remote: Compressing objects: 100% (79/79), done.
remote: Total 115433 (delta 35), reused 1 (delta 1), pack-reused 115353
Receiving objects: 100% (115433/115433), 76.87 MiB | 2.39 MiB/s, done.
Resolving deltas: 100% (79461/79461), done.
Checking connectivity... done.
-----> Checking out chef to 12.2.1
Note: checking out '12.2.1'.

You are in 'detached HEAD' state. You can look around, make experimental
changes and commit them, and you can discard any commits you make in this
state without impacting any branches by performing another checkout.

If you want to create a new branch to retain commits you create, you may
do so (now or later) by using -b with the checkout command again. Example:

  git checkout -b new_branch_name

HEAD is now at 3686402... Bump version to 12.2.1
-----> Installing dependencies
Don't run Bundler as root. Bundler can ask for sudo if it is needed, and installing your bundle
as root will break this application for all non-root users on this machine.
Fetching gem metadata from https://rubygems.org/........
Resolving dependencies...
Using rake 10.1.1
Using i18n 0.7.0
Installing multi_json 1.11.0
Using activesupport 3.2.21
Using builder 3.2.2
Installing ffi 1.9.8
Using libyajl2 1.2.0
Installing ffi-yajl 2.0.0
Using hashie 2.1.2
Using mixlib-log 1.6.0
Using rack 1.5.2
Using uuidtools 2.1.5
Using chef-zero 4.2.1
Using diff-lcs 1.2.5
Using erubis 2.7.0
Installing highline 1.7.1
Using mixlib-authentication 1.3.0
Using mixlib-cli 1.5.0
Using mixlib-config 2.1.0
Using mixlib-shellout 2.0.1
Using net-ssh 2.9.2
Using net-ssh-gateway 1.2.0
Installing net-ssh-multi 1.2.1
Using ipaddress 0.8.0
Installing mime-types 2.4.3
Installing systemu 2.6.5
Using wmi-lite 1.0.0
Installing ohai 8.2.0
Using plist 3.1.0
Using coderay 1.1.0
Using method_source 0.8.2
Using slop 3.6.0
Using pry 0.10.1
Using rspec-support 3.2.2
Using rspec-core 3.2.3
Using rspec-expectations 3.2.1
Using rspec-mocks 3.2.1
Using rspec 3.2.0
Using rspec_junit_formatter 0.2.0
Using rspec-its 1.2.0
Using net-scp 1.2.1
Using specinfra 2.28.1
Using serverspec 2.14.1
Using chef 12.2.1 from source at .
Using bundler 1.7.12
Your bundle is complete!
Gems in the groups server, docgen, test and development were not installed.
Use `bundle show [gemname]` to see where a bundled gem is installed.
-----> Updating appbundler binstubs for chef
Generated binstub /opt/chefdk/bin/chef-apply => /opt/chefdk/embedded/apps/chef/bin/chef-apply
Generated binstub /opt/chefdk/bin/chef-client => /opt/chefdk/embedded/apps/chef/bin/chef-client
Generated binstub /opt/chefdk/bin/chef-service-manager => /opt/chefdk/embedded/apps/chef/bin/chef-service-manager
Generated binstub /opt/chefdk/bin/chef-shell => /opt/chefdk/embedded/apps/chef/bin/chef-shell
Generated binstub /opt/chefdk/bin/chef-solo => /opt/chefdk/embedded/apps/chef/bin/chef-solo
Generated binstub /opt/chefdk/bin/chef-windows-service => /opt/chefdk/embedded/apps/chef/bin/chef-windows-service
Generated binstub /opt/chefdk/bin/knife => /opt/chefdk/embedded/apps/chef/bin/knife
-----> Finished!

# Verify the gem was installed and everything is working correctly
[21:23:42] (26) jreid@JoesMacBookPro:~/repo/chefdk-update-app(master)
$ gem list | grep chef
chef (12.2.1, 12.0.3)
chef-dk (0.4.0)
chef-provisioning (1.0.1, 0.18)
chef-provisioning-aws (0.2.1)
chef-provisioning-azure (0.1)
chef-provisioning-fog (0.12)
chef-provisioning-vagrant (0.8.1)
chef-vault (2.4.0)
chef-zero (4.2.1, 3.2.1, 1.5.6)
cheffish (1.1.2, 0.9.2)
chefspec (4.2.0)


[21:23:33] (25) jreid@JoesMacBookPro:~/repo/chefdk-update-app(master)
$ chef verify
Running verification for component 'berkshelf'
Running verification for component 'test-kitchen'
Running verification for component 'chef-client'
Running verification for component 'chef-dk'
Running verification for component 'chefspec'
Running verification for component 'rubocop'
Running verification for component 'fauxhai'
Running verification for component 'knife-spork'
Running verification for component 'kitchen-vagrant'
Running verification for component 'package installation'
.....
---------------------------------------------
Verification of component 'chef-dk' succeeded.
Verification of component 'rubocop' succeeded.
Verification of component 'knife-spork' succeeded.
Verification of component 'berkshelf' succeeded.
Verification of component 'chef-client' succeeded.
Verification of component 'fauxhai' succeeded.
Verification of component 'test-kitchen' succeeded.
Verification of component 'kitchen-vagrant' succeeded.
Verification of component 'chefspec' succeeded.
Verification of component 'package installation' succeeded.

# Check version at the command line
$ chef-client -v
Chef: 12.2.1