cookbook 'datadog', '~> 2.6.0'

• [FEATURE] Allow multiple enpoints/api_keys conf on Agent and handler, #317 @degemer
• [FEATURE] Add kafka template versioning, #340 @degemer
• [FEATURE] Add gunicorn support, #355 @mlcooper
• [FEATURE] Add attribute to allow agent downgrade, #359 @olivielpeau
• [OPTIMIZE] Fully disable dogstatsd when attribute is set to false/nil, #348 @ccannell67
• [OPTIMIZE] Use HTTPS for yumrepo when applicable, #351 @aknarts
• [BUGFIX] Fix agent version test when version contains an epoch, #357 @olivielpeau
• [BUGFIX] Fix datadog-agent-base removal guard logic on rhellions, #358 @olivielpeau
• [BUGFIX] Replace deprecated properties of yum_repository, #361 & #362 @historus & @olivielpeau