Add alert for sequential reads
A large spike in sequential reads should result in a page https://performance.gitlab.net/dashboard/db/postgres-tuple-statistics?panelId=8&fullscreen&orgId=1&from=1513860152962&to=1513864912593
A large spike in sequential reads should result in a page https://performance.gitlab.net/dashboard/db/postgres-tuple-statistics?panelId=8&fullscreen&orgId=1&from=1513860152962&to=1513864912593