Add documentation for environment variables
Add documentation for environment variables

castiron/puppet-mysql,jcarlson/cdx-mysql,jcarlson/cdx-mysql,theand-boxen/puppet-mysql,boxen/puppet-mysql,castiron/puppet-mysql,theand-boxen/puppet-mysql,castiron/puppet-mysql,boxen/puppet-mysql,boxen/puppet-mysql,Betterment/puppet-mysql,Betterment/puppet-mysql,theand-boxen/puppet-mysql,Betterment/puppet-mysql