Add. Support MD5 libraries `md5`, `lmd5` and `lua-crypto`.
Add. Support JSON libraries `json` and `cjson`.
Fix. Send in response same algorithm as in request.
Fix. Work with my buggy server.

I use server with this requirements:
  * order sensitivity of field in `Authorization` header.
  * `nc` field must be without quoted
Merge pull request #2 from moteus/moteus

Support byggy server.
stop requiring md5: it is in DIGEST now
refactor, make it clear we only support MD5 for now
typo
Fix #5: return nil + error message on unsupported qop or algo
Merge pull request #1 from catwell/master

Marge with base repo