Cleanup in the runtime scripts
Presents embeddables one at a time. [#49877927]

As described here: https://www.pivotaltracker.com/story/show/49877927 This just includes the layout and the scrolling JS; so far there are no controls to trigger the transition, nor admin controls to turn this mode on and off.
Adds controls to the embeddable carousel.

Adds "Next" and "Previous" buttons to allow for user navigation between embeddables in carousel mode. [#49877927]

https://www.pivotaltracker.com/story/show/49877927
Authoring mode control of embeddable display

[#49877927] This introduces a page attribute for how embeddables are displayed, and a form field in the page edit window to control the setting of it.

https://www.pivotaltracker.com/story/show/49877927
Oops: fix a misspelling
Don't show the carousel if there's only one embeddable

[#49877927]
Spec tests for non-JS parts of carousel embeddables

[#49877927]