add support for filename multipart/form-data

filename extensions used in the request are automatically appended to
the url/location in the response.

also includes miscellaneous cleanups and code-deduplication
add file upload to form; prettify form somewhat

nice tweaks to stream selection logic
lazy index update

shows preference for filename/@ over form/< and that we can do binary
over form-data now.
replace static highlight css with new route
add list of lexers via /l
slightly better cache-control

* only mess with GET
* add etags
* conditional (304) requests

By the time we get to add_cache_header, we've already invested a bunch
of time in making this request (and even more to re-sha1). However, this
should at least help varnish quite a bit.
Merge pull request #28 from buhman/filename-form-data

filename form-data
Merge pull request #29 from buhman/pygments-routes

pygments routes
Merge pull request #30 from buhman/etag

slightly better cache-control