TLV capture and parsing for proxy protocol v2

[stu-elastic]

• Adds rawTLVs to Header struct
• API Change
  • non-io.EOF errors encountered when reading from payload reader are returned
    from parseVersion2 and Read
  • Padding is saved in rawTLV
• TLV splitting is implemented by Header.TLVs(), TLV length validation without
  this explicit call
• Includes helpers for parsing AWS VPCEs and SSL information
• Parsing of other types possible by consumers via the PP2Type constants using
  the TLV and PP2SSL exported types

[Freeaqingme]

Given the overlap with #2 I'll see if I can give this code a try later this week and see if it also accomplishes what I was trying to do with #2. Not that that should be the goal in itself, but I'd like to see if - if we start changing the API - can do so with only a single change rather than having to change it multiple times.

[stu-elastic]

I'd like to see if - if we start changing the API - can do so with only a single change rather than having to change it multiple times.

This is a backwards compatible change, if there are non-bwc API changes that are required for #2 then I'd suggest rolling a new major version while letting this go into a minor version release.

[stu-elastic]

Closed in favor of #10

[Freeaqingme]

This is a backwards compatible change

Good point. Though you are extending the public interface a bit, so I'd like to see if it also suffices for my original requirements. Just to see if we can prevent a future BC break. (or at least know so in advance)

[pires]

Maybe it's time to do releases and stop getting this from master. dep/go modules have come a long way.