Upgrade to CanJS 6

[matthewp]

This is an initial issue for DoneJS 4 which includes CanJS 6. I would recommend keeping DoneJS 4 small and possible look forward to a DoneJS 5 for larger changes to the framework.

[matthewp]

I did a spike on this in the last few days. Things done:

• Upgrading major packages such as done-autorender, done-component, done-ssr.

Not done:

• Made can-stache-element work (this requires a new custom elements shim sort of like the MutationObserver one created for DoneJS 3).
• Upgraded donejs-cli / generators.
• Updated demo apps.

I would expect this to be a 3+ week project to complete if we tackle it.