cryptobyte: new package.

cryptobyte is a helper library for building and parsing byte strings,
specifically for TLS and ASN.1.

Change-Id: I046b94773f6781153784c79f3d81e6d464eaebe0
Reviewed-on: https://go-review.googlesource.com/36123
Reviewed-by: Adam Langley <agl@golang.org>
Run-TryBot: Adam Langley <agl@golang.org>
TryBot-Result: Gobot Gobot <gobot@golang.org>
6 files changed