Fix mixed content warning from CSS import

When using https://harthur.github.io/bugzilla-todos/ there is a mixed content warning after https://github.com/harthur/bugzilla-todos/commit/2b0f8500dbbd41a5874aa15e562e3e50c189bc18

10:58:07.263 Blocked loading mixed active content "http://fonts.googleapis.com/css?family=Roboto:400,300,500,700"[Learn More] bugzilla-todos
10:58:07.264 Blocked loading mixed active content "http://fonts.googleapis.com/css?family=Roboto+Slab:400,300,700"[Learn More] bugzilla-todos