Migrate to a mostly rustpkg-driven buildsystem

Unfortunately rustpkg can't yet work with inlined tests, so
the tests are run with the Makefile-driven approach.
Merge branch 'master' of https://github.com/erickt/rust-http into rustpkg
Fix missing docs and tags targets
Merge pull request #40 from am0d/rustpkg

Rustpkg
Remove unused an miscategorised functionality from buffer.

It'll be coming back in better form soon, never fear.
Refactor code, improve invalid HTTP compatibility.

- Refactor common reading methods for more flexibility.
- Make a Request-URI with HTTP-Version and LF only, instead of CRLF,
  work (as recommended in RFC 2616).
Update some goals/design decisions in the README.