Correct highlight of modules in require/import list

Currently only the first module is highlighted in require/import lists, this fix highlights all of them. Note that this does not fix highlighting of submodule imports, so

```
;; sys and pprint are now highlighted, os and path are still not highlighted
(import sys pprint [os [path]])
```
 
These can be arbitrarily nested, so I'm not sure how to go about supporting highlighting in this case.