Implement #to_s and #inspect on all objects consistently

We are currently relying on the `#to_s` method from a location to return it's path. This is a potential breaking change in the future. As part of this fix, we should also fix that...

All objects should respond to both `#to_s` and `#inspect` and deliver the following format:

    $ thing.to_s    => #<Berkshelf::OBJECT (small info, like name or version)>
    $ thing.inspect => #<Berkshelf::OBJECT (lots of info - pretty much the entire object)