Article navigation: next & previous buttons are messed up, + added a way to get titles

Hi Christopher,

I noticed that your implementation of the 'next' and 'previous' buttons isn't really intuitive (at least for me), they navigate in a reverse order -- for example, on your blog clicking the 'next' button will actually open an older article.

I changed it for myself, you might want to do the same if you like.

I also made these functions returning whole article instances so I could show an actual page titles where 'next' and 'previous' buttons are pointing, and I removed cycle between the first and the last available articles.