Generate the link in the header with url_for

This is part of the process of changing over to relative URLs.
Use url_for for the links to the match pages

This is part of the process of switching over to relative URIs.
Use url_for for the return link

This completes the switch over to url_for as part of the process of
enabling relative URIs.
Merge pull request #2 from prophile/relative-uris

Relative URIs