Calendar of Events: added fluid-width display option

The calendar of events should have a fluid-width option, so I made a quick CSS edit to the existing plugin. With this update, you just have to add `cal-responsive` class to calendar containing `div`.

(Note: I updated the examples in English, but not French)
I removed the `div` specificity (coding habit, sorry).

I tried nesting, but I couldn't achieve the desired CSS output:
```css
.cal-cnt-fluid.cal-cnt, .cal-cnt-fluid table.cal-cnt {
  width: 100%; 
}
```

Any suggestions?