Underline the "Release notes" link
Underline the "Release notes" link

The last step changed the color of the "Release Notes" link for better
contrast. This in turn made it hard to identify that it's a link. So,
 underline the "Release Notes" link so that it's obvious that it
is a link.

Also, make sure that this doesn't affect the download link as the current
button-like style looks good already.

mosoft521/gitscm-next,Mokolea/git-scm.com,mosoft521/gitscm-next,git/git-scm.com,mosoft521/gitscm-next,git/git-scm.com,mosoft521/gitscm-next,Mokolea/git-scm.com,Mokolea/git-scm.com,git/git-scm.com,Mokolea/git-scm.com,git/git-scm.com