Prepare for next release 1.6.0

Current Release Review: OPSINFRA-1412
Next Release Review: OPSINFRA-1500
Update the Berksfile.lock and account for new foodcritic ABC metric
Merge pull request #7 from david-crowder/update_berks_lock_fix_foodcritic

Update the Berksfile.lock and disable new foodcritic metric
Added logic to install the universal forwarder on windows

This logic does not support installing any of the server based packages, only the forwarder.
The installation is system level and does not support specifying a user.
Merge pull request #5 from david-crowder/add-windows-forwarder

Add management of a Splunk Forwarder on Windows. 
Also fixes #4
Custom App Doc ideas.
Implement Splunk custom apps hwrp
Updated the cluster_master recipe and added example of master-apps
Don't fail forwarders if they don't have access to the cluster's apps data bag
Merge pull request #11 from david-crowder/custom-apps

Add HWRP for configuring custom apps. 
Also fixes #1
Created CONTRIBUTERS.md
Merge pull request #9 from leslieth/stable

Created CONTRIBUTING guidance.
Release 1.6.0