Fixed thing == <not a Thing> bug

Fixed a bug where comparing objects of type **Thing** is compared to anything else (i.e. **Nil**) would cause **NoMethodError**. Now it just returns _false_.

The actual changes are in lib/redditkit/thing.rb and spec/redditkit/thing_spec.rb. This is my first time doing this so it looks like a bunch of other changes from the VCR files came along for the ride... sorry about that.