Add simple smoother for accelerometer, refactor internals. 

This patch adds only an n-1 blending filter (basically a lo-pass filter) and simplifies the output. 

We can see what the smoother looks like here:

![rplot](https://f.cloud.github.com/assets/390863/640177/9797a476-d2ea-11e2-9fa8-d25089e28499.png)

This is not a dramatic change, but future smoothers will allow for more interesting results. 

A rough overview of the other code changes:

* `iranges` have been dropped as they were only used in the `"axischange"` event and that wasn't even fully implemented.
* The initial check is dropped as we initialize `last` with 0s, allowing both the smoother and the change event to be commensurable.
* output data values don't need to be pre-filled with null as we fill them with `analogRead` or `smoother`. Likewise the axis keys are simply supplied.