Add Roboto to the `$helvetica` font stack for Android support
Add Roboto to the `$helvetica` font stack for Android support

Most Android devices do not have either Helvetica Neue or Helvetica available,
but as of Android 4.0 "Ice Cream Sandwich" there is a look-alike font called
Roboto that serves as a decent stand-in for the (better) Helvetica fonts.

ismarkunc/bourbon,zyj1022/bourbon,jamadam/bourbon-docs-jp,mindeavor/bourbon,chriseppstein/bourbon,jasonwalkow/bourbon,Jazz-Man/bourbon,jamadam/bourbon-docs-jp,Nikeshsuwal/bourbon,jasonwalkow/bourbon,jamesmenera/bourbon-libsass,zyj1022/bourbon,cllns/bourbon,greyhwndz/bourbon,setie/bourbon,nagyistoce/sass-bourbon.io,nickg33/bourbon,jamadam/bourbon-docs-jp,thoughtbot/bourbon,craftsmen/bourbon,smithdamen/bourbon,jamadam/bourbon-docs-jp,jamesmenera/bourbon-libsass,craftsmen/bourbon,smithdamen/bourbon,chriseppstein/bourbon,nickg33/bourbon,san650/bourbon,mindeavor/bourbon,Jazz-Man/bourbon,greyhwndz/bourbon,thoughtbot/bourbon,setie/bourbon