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
Improve error message for invalid URLs
Merge pull request #634 from skoolbus39/RD-Updates

Font-stacks updated to better match glyph size.
Update build dependencies to latest version
Prep for new lessc flags and syntax improvements
Added an environment test to the Makefil
Warns if lessc is not the current required version
Redo pixel alignment in N Flag vector files
Closes #629
Merge pull request #636 from mfairchild365/examples-ie8

Fix Examples in ie8
Revert "code will not be wrapped in #example-code"

This reverts commit 21c28b9a093548db8649585f0e6b026e8745ce6d.