FR: support left/right swap of media and text regions

I have created a modified version of timelineJS that allows for indicating an alignment option on a per event basis, basically in the JSON you indicate "align": "right" to swap the image and content alignment, "align": "center" to center and stack the image and content, or "align": "left" to have the original functionality of image on left, text on right. You can see an example of this here: http://rlacy.tidalwaveagency.com/index.php/history

My current implementation was quick and dirty as we needed to demo the functionality for a client, but I thought I would pitch the idea up and see if there was any interest. If there is, I would be happy to implement it properly via your build system and submit a PR. I have not fully vetted any edge cases but it was a relatively simple modification with only a few modifications to the JS and some new CSS classes.