Empty version number in latest

When downloading the latest build from downloads.corcel.io the version output is empty.  This looks like we are missing a make step.

steps to repeat:

```
> wget https://github.com/guzzlerio/corcel/releases/download/latest/linux_amd64_corcel
> chmod +x linux_amd64_corcel
> ./linux_amd64_corcel --version
Version EMPTY, Build Time: EMPTY, Hash: EMPTY
```