Added multiple new events and widget for embedding into another webpage.

Sorry for so many changes at once, I got a little carried away... :)

I added multiple event types to the github_activity.js library. Specifically:
* CreateEvent
* DeleteEvent
* ForkEvent
* PullRequestEvent
* PullRequestReviewCommentEvent
* IssueCommentEvent
* WatchEvent (starring repositories)
* MemberEvent (adding a member to a repository)
* GollumEvent (creating a wiki)
* FollowEvent (following a user)

I also updated the layout to be more CSS-friendly and to somewhat match the layout of GitHub's public user feed, as well as enabled passing in the parameters for the activity feed through the URL string.
I added a demo page to the repository and made quite a bit of changes to the README.md file.
I created the gh-pages branch to allow anyone to embed the feed (demo index.html) onto their page using an iframe with the link to my GitHub pages account. The instructions for this are included in the README file as well.

You can see a demo of how everything looks when completed at http://blog.caseyscarborough.com/activity/, 
or better yet: http://caseyscarborough.github.io/github-activity/?username=grasuth&limit=25

Also, if you accept the pull request, feel free to create a gh-pages branch and change the URLs to your page instead of mine.