Automatically generate search stubs

When a search is used in a recipe, it generates this error:

```
#<ChefSpec::Error::SearchNotStubbed: Executing a real search is disabled. Unregistered search:
    search(:my_search, "*:*")   
You can stub this search with:
    stub_search("my_search", "*:*").and_return(...)
```

Should catch this exception and create a `stub_search` block in the spec.
