cleanup rewrite_content/fetch_request api to take a full wb_url
add content-length to responses whenever possible (WbResponse) and static files
bump version to 0.5.2
by settings index_paths to '$liveweb'. When used, creates a RewriteHandler instead of WBHandler
Can also specify 'proxyhostport' to set the live rewrite to go through a proxy
fallback: allow fallback to a different handler (usually live rewrite) by specifying
'redir_fallback' with name of handler. Instead of 404, a not found response will
internally call the fallback handler to get a response