make date selection slider more obvious

[tyrasd]

couple of options:

• [x] show date slider all the time and make date bars drap-droppable instead of current click-drag
  • like google finance
  • could be more touch-friendly
  • [ ] what should the initial state of the time selection be? last month/year?
  • [x] check if technically doable with current graphing library (vega)

or just

• [x] add visual hints and/or help text to explain that the time bar is selectable and zoomable

//cc @felskia

[tyrasd]

I've now added a crosshair mouse cursor on the time/experience chart to indicate that there is something selectable there.

Ideally, I'd like to have the boundaries individually adjustable (like in http://square.github.io/crossfilter/), ~~but as far as I can see that would more or less require rewriting the chart code from scratch~~

[felskia]

@tyrasd I think there are two issues:

• making the zoom more obvious
• showing that a user can select a particular area on the timeline more obvious

To make the zoom more obvious I this is fine for now. I think down the road having some kind of help button might be nice. I moved it around from the last comp I attached. But I think when you press the help button it would be nice if it pulled up a modal on what you can do on the site.

For the selection bar on the timeline. I would have the timeline selection bar up so that users can see that it's an interface element. Maybe if you just put it at the very end of the timeline. It would be nice to be able to drag the individual bars but I think the more important part is to have to on the screen upon initial load.