Change font to "TeX Gyre Heros"

  Helvetica and Helvetica Neue aren't available on the stat or biostat
  servers, so I switched to a similar font that one can download and
  install.

  See here:
    http://www.gust.org.pl/projects/e-foundry/tex-gyre/heros/index_html

  Download fonts from here:
    http://www.gust.org.pl/projects/e-foundry/tex-gyre/heros/qhv2.004otf.zip

  Unzip into ~/.fonts/