Font-stacks updated to better match glyph size.

#616
Update .sans-serif-font-weight

I discovered that I accidentally removed the font-weight. This restores
it.
Header update

1. Improves spacing on institution title at all widths
2. Decreases letter-spacing on site title to allow for more characters
at narrower widths
Merge pull request #634 from skoolbus39/RD-Updates

Font-stacks updated to better match glyph size.