Created a miniblog

As a way to write more in my site, and in general, I've decided to properly set the notes category of this blog as a microblog "separated" from the main blog. Had to create some plugins for Pelican to accomplish it, and included the cool way to create slugs I read about in this great blog post by Brandur Leach.

To make sure whoever subscribes to the main blog doesn't get this more "stream of thought" bite-size content, the posts in this category are excluded from the main feed; it has its own feed anyway.