844 - Appending area plot before line during _setup

Close #844.
Removing useless setup definition
Release version 0.26.0
Merge pull request #889 from palantir/release-0.26.0

Merge 0.26.0 into develop.
Remove comments from develop.
Merge pull request #875 from palantir/844-areaBeforeLine

844 - Appending area plot before line during _setup
Respond to Brandon's concerns: improve comments and generic typing
Fix minor type error
Merge pull request #884 from palantir/type-d3-map-set

Add typings for D3.Set and D3.Map
Merge pull request #893 from palantir/develop

Retarget #884 to develop. Use d3 map instead of object in new style plot.