`asdf help` does not work with Homebrew installation

### Steps to reproduce

- `brew install asdf`
- `asdf` or `asdf help`

### Expected behavior

Should list help text for `asdf`

### Actual behavior

```
cat: /usr/local/VERSION: No such file or directory
version:

cat: /usr/local/help.txt: No such file or directory

"Late but latest"
-- Rajinikanth
```

### Environment

**OS**: macOS 10.14.6

**asdf version**: 0.75
