[DOCS] Adds overview for machine learning rules and filters#84

Merged

lcawl merged 3 commits intoelastic:masterfrom lcawl:lcawley-rules

Jul 24, 2018

+40

Commits on Jul 18, 2018

[DOCS] Adds overview of ML rules and filters
lcawl
committed

Commits on Jul 19, 2018

[DOCS] More overview info for rules and filters
lcawl
committed

Commits on Jul 23, 2018

[DOCS] Addresses feedback about rules overview
lcawl
committed