Fix some nasty bugs

While using the apt data and package system to profile degasolv, I found some rather nasty bugs. This release fixes them. This tool is now ready for prime time.

In just ~15 seconds, it slurps in a rather large apt repository Packages.gz file.
In another ~45 seconds, it resolves the ubuntu-desktop package, spitting out a grand total of 797 packages with their locations.

Add the --disable-alternatives flag for debugging

Add the --disable-alternatives flag for debugging purposes. See the docs.

Add `present package` and `package system` options

This is so that I can start to profile degasolv using apt package repos (real-world data) and optimize its performance.

Add standard input as a file type

1.3.0

Add standard input as file type

Add multiple configuration files

This release allows the user to specify multiple configuration files, thus allowing for site-wide configuration.

1.1.0

You can now use degasolv to allow multiple versions of the same package to be used to resolve packages. You can also use it to resolve versions of the package in much the same way as maven using the prioritized conflict strategy.

As a side note, degasolv used to resolve dependencies in a depth-first manner, where it now does it in a breadth-first manner. This is a sort of bug fix; it should have been using breadth-first all along.

1.0.2

This represents the intial release of degasolv.