Immunize URLs against changes to label casing

[osteele]

It's likely (#211) that Final Events will change to final events or final-events.

(Even if we decide on capitalized feature names, we might apply the capitalization in the presentation layer.)

Insure that previously bookmarked URLs such as http://events.olin.build/calendar/academic,featured,Final%20Events,food,holidays,StAR (note the presence of Final%20Events) continue to work in this case.

This can be done by normalizing the elements of state.labels.visibleLabels in calendar-container.js against a map of normalized label names.