Need Help : Installing SugarCRM v7.8

I am new to SugarCRM and trying to install v7.8. I am referring to

https://support.sugarcrm.com/Documentation/Sugar_Versions/7.8/Ent/Installation_and_Upgrade_Guide/

During the installation, "Database Configuration & Elastic Search page", I am getting an error

Warning: require_once(vendor/ruflin/elastica/lib/Elastica/Connection/Strategy/StrategyFactory.php): failed to open stream: No such file or directory in /var/www/html/sugarcrmdev/include/utils/autoloader.php on line 360

Fatal error: require_once(): Failed opening required 'vendor/ruflin/elastica/lib/Elastica/Connection/Strategy/StrategyFactory.php' (include_path='/var/www/html/sugarcrmdev:/var/www/html/sugarcrmdev/vendor:.:/usr/share/pear:/usr/share/php') in /var/www/html/sugarcrmdev/include/utils/autoloader.php on line 360

I found that Connection/Strategy/StrategyFactory.php does not exists.

I have installed Elastic Search v1.7.5 using rpm as per supported platforms page and verified the version as well by hitting "http://localhost:9200".

I had a look at support page as well,

https://support.sugarcrm.com/Knowledge_Base/Installation_Upgrade/Installing_and_Administering_Elasticsearch_for_Sugar_7/… 

i dont have the file "elasticsearch.yml" as well.

So, probably, i am missing some pre-installation step which I am not able to figure out. Can someone please guide me as to what i could be missing.

thanks a lot.