[Layout] Top Navigation bar links

[carbontwelve]

The current top navigation bar is very sparse containing just three links:

• the logo
• documentation
• download

It's not immediately visible from these links that the project is available on github and due to the push with #43 away from the phar distribution (towards composer) the download link should be a lower priority if not relegated to the install documentation page as one method.

With the new addition of the Tapestry Boilerplate project there will soon be a number of starter "themes" for people to begin using Tapestry quickly. It would be nice to have a section that listed those like hugo do here.