Resolve longest match first

Given:

```
moduleAlias.addAliases({
    "react-dom": "preact-compat-enzyme",
    "react-dom/server": "preact-render-to-string"
});
```

An attempt to `require('react-dom/server')` yields `Error: Cannot find module 'preact-compat-enzyme/server'`.

I believe the simple solution would be to evaluate possible matches, and choose the longest.