Add ability to have multiple instances

[wpscholar]

Request:
"Can more than one instance (that pulls in different posts and post_types) be used on the same and/or different pages? It looks like there's only one set of entries in the options table, not one set per unique page."

It would probably be ideal to have the ability to set an "ID" on the post type that serves as the unique ID for a collection of entries that should be displayed. This ID would have a default value so that if it isn't provided everything will work the same as it does now.