upgrade to roboto 2

Move to using Roboto 2. Also, remove a workaround for font rendering issues on windows (#2517). Will double check this manually after the build goes through.

@ussuri 
I see. It looks like it's the only currently available format right now because it's primarily meant for desktop usage. A WOFF version should appear on Google Fonts eventually: I think we should switch to it then, for the size/speed benefits. For now let's go with TTF.