Dev

I'm sure this will require quite a bit of discussion before it may or may not be added to the library. The animation plugin (would be) requires quite a bit of work as it currently contains copies of some of the functions from impress.js. This is because I wanted to keep the animation framework separate from the impress.js file. I was hoping to find time to refactor it into something that could be passed into the impress.js init as an option of sorts. This is my first time making a pull request on github so I hope I'm going about this correctly. The substep changes could probably benefit from some codereuse reduction. It may seem slightly chaotic as I got stuck at a certain point and seeing as how I also wanted to finish the presentation. Hope I can clean this up and if you're interested I'd gladly contribute my work to the benefit of the impress.js project.