indentation with go fmt

Thanks for releasing the packer post-processor!
One of the first things I have learned in Go is to use the builtin indentation (although it might look different to other languages using tabs instead of spaces).

So, what I did in this PR is just a

```
go fmt
```

to the source tree. I currently use Sublime with GoSublime plugin which also just does a `go fmt` when saving a go source file.

Further reading on [stackoverflow](http://stackoverflow.com/questions/19094704/indentation-in-go-tabs-or-spaces), there are links to the official indentation guide which also has some tips for vim and other editors.