basic area/line/bar and stack functionality for stacked

well, it's not really stacked any more, but that comes later

add the ability to set the renderer and or toggle stack on stacked graphs

add a alpha filter if showing an unstacked area, so any graphs that overload each other are visible.
Add button to toggle renderer if graph is stacked
Add navbar dropdown helper, and use for graph dropdown
Add UI defaults for render, stack
Change relative time toggles to use dropdowns and new helpers for a cleaner navbar
Update spec and include 'now' selection for stop
rm debug call
Merge branch 'master' into areabarline
Use "on/off" as stack default, not true/false
formatting
Use "on/off" not true/false for stack default
Show stacked selection if using a render other than line
Merge pull request #17 from anchor/areabarline

Merge new stacked area/bar/line functionality