Check main font-stack

[ffoodd]

We're currently using Helvetica Neue on top of native font stack, which should be questionned since:

• Helvetica Neue and Arial are duplicated;
• quotes around font-family names are unnecessary;
• add Liberation Sans to ensure Ubuntu users will get a decent Arial fallback, regardless of the browser they're using — see fontfamily.io page about sans-serif;
• And speaking about Helvetica, should search after webfonts.fonts.com to know if we shouldn't be trying to use local version of Helvetica Neue already?
• Also, consider using font-synthesis since it could prevent faux-bold for example.

[ffoodd]

About the useless quotes:

• Matthias Bynens wrote about "unquote font family names in CSS" back in 2012;
• and went with a neat tool to check wheter your font-family name requires quotes or not
• FWIW, Bootstrap mentions using StyleLint rule to check quotes in family names but it seems to not be set to where-recommended now. I didn't have to change this rule when removing quotes, so…

[ffoodd]

About local() version of Helvetica Neue:

• Peter Gasston wrote an excellent post about "checkking for installed fonts with @font-face and local(),
• and hopefully Adobe has an extended PostScript Name List document.