Improved color contrast of sg-header links.

The default link colors in the sg-header navbar are very difficult to see until hovered over with a mouse. This pull request changes the color from $sg-secondary (808080) to $sg-tertiary (dddddd).

This pull request also has a bunch of other changes caused by my editor settings: it removes whitespace from the end of lines and makes sure each file has a newline character at the end of the file.