Better file handling for reporters (fixes #48 and #57)

Two main changes:

- Instead of deleting an existing report file, it's simply overwritten (see #57)
- The [file](https://www.npmjs.org/package/file) module is used to resolve paths, supporting the use of home (~) in reporter paths. (see #48)

**Something weird happened with this and it's picking up some previous commits. Will Fix**