Countdown tweaks

Summary:
A few tweaks to hsb's Countdown implementation:

• Allow the page to be rendered "chromeless", suitable for display on one of

the dozens of monitors everyone has laying around.

• Show title of countdown in deletion dialog.
• When creating a new countdown default to time(), not Dec 31, 1969.
• Add extra "/" after editing to avoid needless redirect.
• Tweak some page titles.
• Show countdown author in list view.
• Highlight tab in list view.
• Tweak menu copy.
• Link countdown title in list view, separate buttons into different columns

so they pick up padding.

Test Plan:
Created, edited and deleted a timer. Viewed a timer and toggled chrome mode.
Viewed timer list.

Reviewed By: hsb
Reviewers: hsb, aran, jungejason, tuomaspelkonen
CC: aran, hsb, epriestley
Differential Revision: 454