Skeleton log decoder.

This initial commit supports basic decoding of logged HTTP/HTTPS
traffic; the actual parsing is implemented using scodec, along with a
custom (and rather ugly) regex codec implementation to support parsing
non-binary data.
Fix out-of-date string codec test.
Handle empty bodies with no Content-Length (e.g., GET).
Add BouncyCastle for CMS parsing, et al.
Add a zlib compression codec.
Add a CMS Signed Data codec.
Add a base64 codec.
Stub out working decoding of HTTP -> CMS -> Base64 -> ZLIB -> String.
Add Argonaut for JSON handling.
Handle zlib underflow errors.
Normalize the API structure for most of the common codecs.
Move CMS handling into the codecs package.
Add top-level SSLsplit codec API.
Add support for HTTP 'chunked' encoding.
Update for compatibility with the new codec API layout.
Merge branch 'protocol_decoding'
Explicitly enable implicit conversions
Implement parsing of net-monitor's SSLsplit log path format.