Encode/decode changes into a url for sharing

[argyleink]

Once #371 lands, the techniques / functions could be used to encode the changes into a string that's put into the URL. when that url get's shared and visbug get's launched, it can resume that state, applying the necessary styles so someone can see the changes on their machine.

could be interesting for small tweaks! would be cool if visbug was the proxy for packing and unpacking webpage changes.