Fixed: page navigation works, based off diva-body midpoint

-Moved "vida-svg-wrapper" creation to vida.js file for clarity's sake.

-updateCurrentPage will now determine based off vida-body midpoint rather than top.

-next arrow correctly toggles visibility and associated code responds correctly.

-one last change to reflect 0-indexing
New: orientation switching re-enabled, Verovio reloads on resize

-Re-enabled orientation switching

-Updated toolkit JS files

-Added ignoreLayout setting

-Verovio reloads when page has not been resized for 200ms or so

Resolves #3
Resolves #11