Rewrite

This is a near-complete rewrite of the package, with breaking changes.
 - The library now makes far better use of net/http, with no separate Client/Server structures.
 - The rewritten version currently supports SPDY/3, but support for SPDY/2 and SPDY/4 is upcoming.
 - This version fixes the memory leak that was taking place in the existing library.
 - Full documentation of the new library will arrive shortly.