Fix "not expr1 in expr2" warnings
Fix "not expr1 in expr2" warnings

Example warning:

```
warning: "not expr1 in expr2" is deprecated. Instead use "expr1 not in expr2" if you require Elixir v1.5+, or "not(expr1 in expr2)" if you have to support earlier Elixir versions
```

rrrene/credo,rrrene/credo