if category, then include a neat snippet

[dreamalligator]

Proposing that if a post or page is in a particular category that certain snippets are included.

Examples:

• If page or post is in the code category, that a pure CSS "Fork Me" ribbon appears on the upper right of the page. See an example here implemented with Jekyll.
• If page or post is in the event category, that a link to the calendar is appended to the article, with a list of upcoming events. Related Issue, #20.

[dreamalligator]

Implemented pelican-plugins/neighbors for next articles for each article. If event category, then does next event.

I think it looks kind of bulky, got suggestions? See example here: http://sfsu.acm.org/awesome-web-hackathon.html

• https://github.com/acm-sfsu/pelican-cait/commit/c6bce7e59b8259f2901f1ed1ed4eaf62effb420c
• https://github.com/acm-sfsu/acm-sfsu.github.io/commit/461fe3ae4adbe2c56da94f2a5ee7c50ee0c1b4ff