Draw events to timeline based on start time and row number

Fixed issue #48. One _kind of_ breaking change: I added a row field to the event JSON that helps determine where to draw the block. I can just add in a check for the row member as a work around, but I'll wait until you guys take a look. Details are in the code--I'm going to add some comments to the PR so you can see everything that's going on.

Expected behavior: row heights should all be uniform, and event blocks should be placed neatly inside of the rows.

Here's a screenshot:

![screen shot 2014-10-25 at 2 46 16 pm](https://cloud.githubusercontent.com/assets/6354033/4781214/7dca60a2-5c90-11e4-8155-bc539c8d7c91.png)