Popover now matches mock from design.

Specifically the spacing within the popover has been tighetened up. 30px
overall height, 10px horizontal spacing between the elements. The arrow
is now 3px height and 10px wide.
Merge pull request #213 from kadams54/popover-style

Specifically the spacing within the popover has been tighetened up. 30px
overall height, 10px horizontal spacing between the elements. The arrow
is now 3px height and 10px wide.

For reference:

https://launchpadlibrarian.net/168947326/Juju-Tooltip.png