Allow tar to use --strip-components form unarchive

This patch adds an option to the unarchive module
- strip_components=N
which adds --strip-components=N to the tar command line when
unarchiving tar archives.

  ---
  - name: Unpack archive with stupid internal structure
    unarchive:
      src=path/to/archive
      dest=/path/to/archive/unpacked
      strip_components=1