Add a vertical prop to the Tabs component to keep it always vertical

[jaredcwhite]

Currently the Seeds Tabs component switches from horizontal tabs to vertical tabs based on a mobile breakpoint. That's fine to have for some use cases, but for other use cases we need tabs which are always stacked vertically (perhaps living in a sidebar).

Thus we should add a vertical or verticalOnly or keepVertical (some naming ideas, feel free to comment) boolean prop to Tabs which would override the media query-based CSS and keep the tabs vertical no matter what the screen size. That way the author of the template which consumes the Tabs component can choose if they want this functionality in that particular case.

[jaredcwhite]

This would likely solve the need that prompted #73.

[sarahlazarich]

we can use tabs for the account sidebar since it's a simpler implementation than menu

[jaredcwhite]

Just adding a note here we'd also need to incorporate a layout where the tab panel is the right of the tabs, not below (so the tabs actually are in a sidebar). Right now tabs are always directly above the active tab panel no matter what.

[sarahlazarich]

no product QA needed until account screens are built out