Added notes to self feature

Posts tagged "notestoself" are meant to be used for personal reference and are somewhat less publicly visible than normal posts. They won't show up on the front page, the yearly or monthly archive pages, or the latests posts Atom feed. The tag "notestoself" won't show up in the lists of tags in the sidebar. However, posts tagged "notestoself" will still show up in the pages for a given tag (e.g. "Posts tagged ruby" if it also has a tag "ruby") and they will still be searchable by Google.