[fix bug 1106279] Only show dev firstrun doorhanger if tab is visible on page load
extend Chinese Lunar Calendar to 2017
Fix bug 225639 - use relative font sizes
Use new REM-enabled font-size mixin
Bug 225639
Holiday Calendars -> URL to SUMO out of date
Bug 1107679
Merge pull request #2572 from infinet/Extend-Chinese-Lunar-Calendar-to-2017

Extend Chinese Lunar Calendar to 2017
Add documentation for .font-size() mixin
Merge pull request #2555 from alexgibson/dev-edition-firstrun-doorhanger

[fix bug 1106279] Only show dev-edition firstrun doorhanger if tab is visible on page load
Merge pull request #2570 from mozilla/bug-225639-relative-font-sizes

 Fix bug 225639 - use relative font sizes