Move external font css

[egoist]

For the first line in cdn/path/to/vue.css:

@import url('https://fonts.googleapis.com/css?family=Roboto+Mono|Source+Sans+Pro:300,400,600');

Maybe move the style to 404.html to make it customizable, or any better idea?

[QingWei-Li]

I think it should be part of the theme 😅

But I provided a pure.css theme in 0.3.0, it is easy to customize.

[egoist]

At least replace https://fonts.googleapis.com with something accessible in China 😂

[Justineo]

@egoist AFAIK https://fonts.googleapis.com is accessible from mainland China right now.

[QingWei-Li]

Okay, I closed it.