[#14] Set package file permissions based on source

- Verified that the destination files and directories now retain the
  original permissions of the source.
- HOWEVER:
  - Zip format does not honor file permissions, no matter what.
  - PharData appears to use a umask when creating the directory
    structure, which means that directories always get 0755, and not the
    permissions actually set.
  - Individual _file_ permissions _are_ set correctly inside PharData.
Merge branch 'feature/14'

Fixes #14 (kind of)