Replaced miniz with LZMA2.
Changed the package format and made dudepack read from stdin.

This is a smart move, because:
  - It allows extraction of packages with tar.
  - It makes the new dudepack much simpler.
  - It makes it easier to support multiple compression types.
Added a magic number.

This makes it possible to detect attempts to read a random file as a package.
Removed dudeunpack's dependency on SQLite.
Made the repository URL configurable at run-time.
Added a lock file.

This makes it impossible to run multiple instances of packdude in parallel.
Added a dudepack usage example.