add logic to only have one version of an item.  append new tags and categories to original version of an item.
Merge branch 'master' of https://github.com/ReadUpCode/readup
add logic to register an upvote for any item submitted more than once
Merge branch 'master' of https://github.com/ReadUpCode/readup
cast an upvote for the user who posted the item
Merge branch 'master' of https://github.com/ReadUpCode/readup
Merge branch 'master' of https://github.com/DougKong/readup
clean up code by making functions for adding tags and categories to an item
Merge pull request #71 from DougKong/master

add logic to keep each item unique.  all tags, categories and votes will be tied to that unique item.