plottable.js split into multiple files for debugging

As per #295, this diff compiles files individually, rather than into one giant plottable.js. This means that `console.log`, exceptions, and `debugger` will show up in their respective files rather than some random line of plottable.js.

![screen shot 2014-05-29 at 2 02 34 pm](https://cloud.githubusercontent.com/assets/3344958/3123621/a234e37c-e774-11e3-8613-07fc1a904801.png)

The way to get these files is to replace
```
<script src="../plottable.js"></script>
```
with
```
<script src="../plottable_multifile.js"></script>
```
in any new quicktests you make.