No more duplicate widgets

Pretty much what the title says, no more duplicates. When there was more than one github repo tag in the file, the githubRepoWidget js file would get run more than ones, creating additional widgets where there shouldn't be.

Unfortunately, installation is a bit more of a pain now, but I've updated the README to reflect that. Hopefully, it shouldn't be too crazy. If imathis/octopress ever transitions to jQuery, this will need updating.

Closes #2