Modify coappearances method to accept new options.

The :id option adds the ability to limit results to only characters that coappear with the character with the given id. The :return_top option enables returning only the top n links in the network, sorted by link value (weight).
Remove outdated script element.
Remove outdated CSS link.
First pass at displaying character associations.

On each character's page, show a list of the top 10 people that most frequently get mentioned alongside them.
Fix aliased variable name.
Order by decreasing weighted degree.
Update gems.