move-form has the possibility of creating invalid namespaces

If you have the files

```
(ns website.views.analyse-repo
(:require [hiccup.core :as h]))

(defn index [name]
(h/h name))
```

and

```
(ns website.views.layout
(:require [hiccup.page :as h]))

(defn other-func []
(h/html5 "OK"))
```

and you use move-form to move `index` to `layout.clj`, then the resulting namespace in that file will be

```
(ns website.views.layout
(:require [hiccup.page :as h]
[hiccup.core :as h]))
```

Maybe clj-refactor should offer to fix that when it happens?

However, that sounds like it's probably very troublesome to implement. If that's the case, it would be nice to at least get a message about that before or after I make the move, instead of finding out with an evaluation error further down the line.