log more information about failed requests
add nbviewer git info to footer
get the proxied IP in request logs

instead of logging the load-balancer IP
handle more cases in failed upstream fetch

- turn 599 (tornado client) errors into 400, 404, not 502
- turn 4XX in 400, not 500
move log_request to nbviewer.log
Explicit 404 on base64 data-uri requests

seem to come from super-old browsers
hash urls as key to memcache

there is a limit to the length of a key in memcache
tornado already supports xheaders, just needed to turn it on.
Quote URLs. Fixes #145.
Encode URLs for the GistHandler
Merge pull request #143 from minrk/logger

Some more logging changes
Merge pull request #146 from rgbkrk/escape_in_dir

Quote URLs. Fixes #145.
fix commit url in template
Merge pull request #144 from minrk/cachekey

hash urls as key to memcache
self.short_url typo
turn any exception rendering a notebook into 400

not just NbFormatError

And only show tracebacks on the non-nbformat errors.
Merge pull request #147 from minrk/invalid-notebook

turn any exception rendering a notebook into 400
submodules don't have html_url in tree view
Add 'View on GitHub' link to list views
Merge pull request #148 from minrk/listings

listing fixes