docs(app): adds roboto font

The Google Material design docs at http://www.google.com/design/spec/style/typography.html state that we should use the font 'Roboto' for our Typography. I went ahead added the font using @import, but we could also download the fonts and add them to the project. I'm fine with either way.
(From the little stuff that I know about CSS) I don't think we need this.
Basically, we should either have the _@import_ or _@font-face **with a url**_.

Do I miss something ?