Epoch bump for golang-github-valyala-fasthttp

[Guillem Jover <gjover@sipwise.com>]

Hi!

The golang-github-valyala-fasthttp package used to have date-based
release numbers (current Debian version 20160617-2). Upstream has
since switched to semver (latest upstream version 1.31.0).

So the version scheme has been reset, and unfortunately given that no
prefix was used when initially packaging this, an epoch seems to be in
order now.

I'm planning on updating in the coming days to the latest upstream
release and bump the version using an epoch.

Thanks,
Guillem