A few more design tweaks and linting warning fixes

### Design changes
 * There's a small left and right border on the main content when the screen's smaller than the max width (i.e non-desktop or tablet)
 * Changed the title to `Event calendar` instead of `Design event calendar` until there's an actual separation between dev and design calendars.
 * The graph now doesn't recalculate itself on the window resize but instead is always a set size with horizontal scrolling

### Linting
Just a few tweaks to stop JSHint complaining