Git-ignore .yml data dumps
Fixing setting of @sequence and @sequence.theme
Improved display of HAS sequence navigation menu

For [#51593657]: now that the menu shows sequence activities, we see the current activity as a blue "button" and its pages in blue; all the activity blocks have a pseudo drop-shadow. Also content from the page beneath (e.g. the Facebook like icon) is hidden by the menu. Still missing: the arrow glyphs next to the activities and the "MENU" text; the top bump-out indicator; a gradient on the current-activity background to give it button-like texture.

https://www.pivotaltracker.com/story/show/51593657