gqaj (pretty-print) should respect expandtab

I've configured my indentation whitespace settings to match what my team likes (tabs).

```
:set expandtab?
noexpandtab
```

When I use gqaj in a json file, the indenting tabs are replaced with two spaces (shiftwidth is respected).

https://github.com/tpope/vim-jdaddy/blob/master/autoload/jdaddy.vim#L147 seems relevant