Improved error message for missing logstash_version
Improved error message for missing logstash_version

Added a comment that the version needs to be set in the config
jlambert121/beaver,timstoop/python-beaver,doghrim/python-beaver,jlambert121/beaver,python-beaver/python-beaver,davidmoravek/python-beaver,rajmarndi/python-beaver,rajmarndi/python-beaver,Open-Party/python-beaver,PierreF/beaver,imacube/python-beaver,Open-Party/python-beaver,josegonzalez/python-beaver,imacube/python-beaver,josegonzalez/python-beaver,doghrim/python-beaver,davidmoravek/python-beaver,PierreF/beaver,timstoop/python-beaver,python-beaver/python-beaver