Change nav elements to anchor tags.

[keipes]

Changes navigation elements to nachor tags, so broweser specific functionality like open-in-new-tab can function.

Fixes #57

[keipes]

• Tested that links work locally (win 10) in Firefox and Chrome.
• Tested that both the right-click open, and direct click work.
• Made sure each link went to the correct resources.

I understand that this will create additional requests to your backend if a user decides to right-click open a tab rather than directly click it. Allof the resources you're serving are static though, so that should result in a 304 cache hit most of the time.

[Miffyli]

LGTM! Thanks for providing this convenience function :). Perhaps this will work as a basis/template for doing per-game open-in-a-new-tab buttons.