Fix build errors.

I was seeing errors like the following:

    [11:46:18] ERROR: while rendering page 'content/blog/2011-01-20-debugging-monit.txt'
    [11:46:18] ERROR: erb filter error: "uninitialized constant Webby::Renderer::CGI"

This was due to a call to `CGI.escapeHTML` within the default template.