Update elasticsearch.md
Update elasticsearch.md

Added link to a great tutorial page
fannarx/2014-T-514-VEFT,reykjavik-university/2014-T-514-VEFT,reykjavik-university/2014-T-514-VEFT,fannarx/2014-T-514-VEFT,reykjavik-university/2014-T-514-VEFT,fannarx/2014-T-514-VEFT,reykjavik-university/2014-T-514-VEFT