The -version (-v) broken after the new release method

In `hcl2json_Linux_x86_64.tar.gz` for v0.6.6 the `-version` (`-v`) doesn't show the version correctly.

```
$ wget https://github.com/tmccombs/hcl2json/releases/download/v0.6.6/hcl2json_Linux_x86_64.tar.gz
$ tar -xzf hcl2json_Linux_x86_64.tar.gz
$ ./hcl2json -v
devel
```

Also, along with the binary, an unupdated `CHANGELOG.md` for v0.5.0 is bundled quite unnecessarily.