- Support all basic pattern forms: file, directory, *, ?, !

- Fix handling of wildcard patterns and subdirectories - `*/a.py` should
  match `foo/a.py`, but not `foo/bar/a.py`

- Fix handling of directory patterns with a trailing slash - make sure
  they're handled equivalently to those without one

- Fix handling of custom Dockerfiles - make sure they go in the tarball
Signed-off-by: Aanand Prasad <aanand.prasad@gmail.com>