Bug 972666 - [Calendar] lines over events longer than 2 hours

2nd try. now I hope it should NOT fail on Travis anymore.

the only change from previous PR was:

```diff
diff --git a/apps/calendar/style/ui.css b/apps/calendar/style/ui.css
index 6930fd8..c908cd4 100644
--- a/apps/calendar/style/ui.css
+++ b/apps/calendar/style/ui.css
@@ -350,7 +350,7 @@ section.month #month-days ol {
 }
 
 /* Make the rows a bit taller for larger resolutions */
-@media (min-device-height: 640px) {
+@media (min-height: 640px) {
   section.month ol {
     height: 6rem;
   }
```

the media query was being triggered for no reason and causing the defect.

error only started on March because calendar displays 6 rows (on Feb it only needed 5 rows).