Minor refactor and started adding simple tests for parsers.

Still working on these tests, but got a good base for ImportParser.
Might want to check my last change to Config. I return early if there are no args, because I was getting the following error when I create a Config object in my tests:

```
ERROR: massive.munit.UnhandledException: Invalid field access : lastIndexOf at as3hx.parsers.ImportParserTest#testWildcard as .../std/haxe/io/Path.hx
```