Support JDK6 by removing nio.Files (and remove move/copy support for directories)
fixup! Support JDK6 by removing nio.Files (and remove move/copy support for directories)

- Use ResultT.fail instead of sys.error
- Fix checking of src for directory (instead of target)
Introduced ResultT.unit
Introduced ResultT when/unless
Merge pull request #26 from ambiata/cofarrell/jdk6-support-no-dirs

Support JDK6 by removing nio.Files (and remove move/copy support for dirs)