High memory and cpu usage for loadchart widget

[felixhageloh]

You probably saw this one coming :)

So I noticed very high memory usage and cpu spikes when I used this widget. I rewrote it a bit to solve these issues and made a gist: https://gist.github.com/felixhageloh/f6e208a275b458169ac2.
I made it a gist and not a pull request because I'm not 100% it does the same as the original (mostly when it comes to scaling and animations). So I thought maybe you can use this more as a reference. In a nutshell, what I changed is:

• not using local storage to store loads. Also making sure that the array of loads doesn't grow indefinitely
• not deleting an re-creating all bars on every update. Existing bars are re-scaled if necessary. The rescaling is still somewhat slow and there are probably cleverer solutions for it.
• using css scale to control bar height. This makes it faster to animate

If you have feedback or questions, let me know!