Site.Master: "About" → "About Us"

Also prepared a link to rowing.aspx in the header for the future
Merge remote-tracking branch 'origin/master' into 501(c)(3)
Mentioned 501(c)(3) on the "About Us" page.
Updated the Title property on the "About Us" page
Merge pull request #21 from scrc/501(c)(3)

501(c)(3)