tag buttons go invisible after clicking

[ajx42]

The tag buttons become invisible (but they are still there and can be clicked) upon clicking once and coming back to the page.

Locally I made a minor CSS fix. But I am not sure if this is really a bug. I think changing the color to some lighter shade of grey after visiting is better instead of making it completely white.

[atecle]

@FireWithin Noticed the same thing and made a PR - #32

I think it's a bug, visited links are currently unreadable