Fixed missing style specification for home paginator.

Howdy!

I was checking out the brand new version of Hikari a while ago and I seriously gotta say that I love all of the changes! However I found out that the new SCSS files are missing specification for style of main homepage paginator which causes the buttons handling page redirection to look pretty ugly. So here I am with hotfix... :)
Should this be [`$border-color`](https://github.com/m3xm/hikari-for-Jekyll/blob/master/_scss/base/_variables.scss#L10)?