Added avatar tooltips to cards to identify assignees
Gave the tooltip border color and slimmed it down
Added HbAvatarTooltip component and template to unify tooltip styles over avatars (TODO: fix broken _tooltips.sass styling, positioning is broken)
Tweaked tooltip positioning
Fixed filter tooltip from flying away
Merge remote-tracking branch 'origin/discorick/team_member_hover_in_card_shows_username'

Conflicts:
	app/assets/javascripts/board/application.js